I was being a bit of an arse, but my point more so than anything was that if it was to take something away from a recent 4x title, its to release a game thats coherent and achieves what it tries to do (from a gameplay point of view) without needing to wait several years for the complete game. Regardless of whether people like the game or not, the game was released stable (I haven't heard of or had to deal with bugs since full release), and every mechanic feels woven together well. It can indeed feel jarring to go from Civilization to Old World and see cities restricted to pre-placed city sites, but even then they've managed to implement it in a way that contributes to the game (competition with bots for sites, forcing military investment at risk of being overshadowed by everyone else, and forcing interaction with the tribes). It also offers a FANTASTIC UI loaded with every bit of information you could ever need IN GAME. Again if it was to take something away, a UI which provides you with all the information you could ever need would be fantastic, and they should NEVER take anything with regards to UI and clarity of gameplay from Humankind. To be fair the UI in Civ wasn't bad though, so this is probably something they can competently do anyway. I haven't played Civ 6 in a while so can't really remember.
If I was to take things from each game and implement them into Civ:
From Old World:
-Dividing 'Production' into different areas, giving you reason to specialise cities towards the different needs of your Empire/Civ. The way Old World does this is to split 'Production' into 'Growth', 'Civics' and 'Training'.
Growth is used to produce your civil units (Workers, Settlers, Caravans (if your city can do that), Scouts and Militia).Civics is used to further develop the City through training Specialists (essentially something that consumes Citizens and grants a buff to a specific tile where the specialist is trained), building certain Buildings (these grant an immediate gain of some sort and grant turn-by-turn yields, for example Treasury grants you gold per turn and a larger lump sum of gold when built), and perform Projects (these consume civics, and upon completion grants a lump sum of some resource; these are repeatable).Training is used to build your Military Units.
The way Old World does this smartly ensures that these 'Production' equivalents do something for when they aren't in use. Civics accumulates globally, allowing you to spend it to enact laws or perform various actions based on the characters you have in your empire such as conducting diplomatic actions. Training also accumulates globally, allowing you to spend it to Force March your units, exchange it for orders, or force promote your units before they've accrued the correct amount of xp for the level up, among other things. Growth translates into increased Citizens (Old World does this weird thing where for the majority of the early game Citizens are bad unless you train them into Specialists, until you get to building the final tier of certain districts which buff Citizens to giving yields. Otherwise they provide miniscule amounts of Orders and cost Upkeep to maintain).
Civilization doesn't need to copy paste this system, but I really think Civilization should consider creating more deliberate uses for cities, which influences specialisation of cities, whilst also not feeling terrible for not continually putting cities to use (in fact passively allowing a city to do nothing should be in itself a conscious choice made by the player, which takes this concept further). I do think distibuting 'Production' between several resources would contribute to this. How could Civ do this? I would personally make it so the yields of tiles translate into these 'Production' yields. Maybe have 3 basic yields on tiles: Food, Industry and Curiosities. Food would be consumed by the upkeep of cities, or by the production of civilian units, and translate into Growth when not in use. Industry would be used to construct your key districts and buildings, and translate into Gold when not used (IE leaving cities alone could translate into rapid development of other cities). Curiosities would translate into conducting Projects, potentially enacting Edicts or establishing some kind of Tradition to specialise the city, and translate into alternate global resources based on the infrastructure in place in the city (IE Cities with Campuses would convert Curiosities such as a local crater or mountain range into Science; whereas Holy Sites would see Monks/Priests inspect and derive faith from these same sites). Military Units would consume a mix of Food and Industry, ideally starting with a larger percentage of cost levied towards food, and then slowly transitioning towards being more Industry intensive. Obviously game devs are much more adept at how to consider and implement such systems, but I was just trying to give an example of how it could look.
-Scouting being exciting. Scouts in Old World accrue resources for you by merely exploring, as they catch sight of bonus resources/luxuries they net you either food, stone, metal, gold, or wood (not sure about wood or gold to be honest but I think they do).
Goody huts in that game always results in events (unless you use the map editor to cheat in more to the point the events get exhausted, after which they give you large lump sums of resources). These events are FANTASTIC, giving you choices you really have to consider. Many have downsides mixed in with the ups. Events in general are an iffy area when it comes to civ, and they'd need to be tailored to civ, but I really would love to see their inclusion.
Scouts can also 'harvest' certain resources, putting that tiles resource on cooldown, and netting you some resources, whilst also potentially triggering an event.
When the scouting phase is over, you can use them to keep eyes on other factions (made viable as they go invisible in forested tiles), and they can be used to infiltrate cities, essentially becoming the equivalent to spies in the late game.
All of this is an excellent use of a single unit which falls off significantly in most other 4Xs. Humankind reaction to this was that they somehow upgrade into Cavalry units, which felt weird and made an already OP build up a scout army in the Neolithic Era more powerful. In Civilization you just lose interest in your scouts (at least I do, I'm not speaking for others). I certainly hope Civilization develops each unit AND component to have the longevity they do in Old World. And I would love to see them work on Scouts to make them more exciting. Exploration is one of the 4Xs afterall.
As with dividing production none of this needs to be a copy paste system. Accruing resources by merely exploring most likely won't work in Civilization due to the way yields work (Old World treats a lot of yields more like you would see in a traditional RTS; you accumulate it and spend it to build things, the Production yields determine how fast). In fact in Civilization it wouldn't need to have this sort of system as there is no Order system to act as a limiter to your activities (IE there is no opportunity cost involved in Scouting outside of the construction of the Scout, and I suspect this is why they implemented that system of exploring yielding resources (remember when I said well woven mechanics)). However, evolving scouts to eventually continue on as a spy-like unit, and continuing the need for recon would be lovely. Heck in Civ6 I found it weird that they had this perfect unit available which could enhance artillery, but you needed a dedicated unit for it instead of using a very logical already existing alternative?
What I would not want from Old World:
-The Orders System. Its probably the best thing they added, BUT, its not a Civilization mechanic. There are huge advantages to implementing it, namely making each action more considered and loading each turn with opportunity cost, however, I can't see it scaling well over multiple eras without it becoming inconsequential by the late game. Furthermore, I do think Civilization should retain a lot of what makes Civilization... Civilization. The Orders System is a huge change to how the game normally functions.
-The Characters System. This one I think is obvious. Its an integral component of Old World, but this just won't work in Civilization.
From Humankind:
-Verticality. I think this is probably the one thing we will almost certainly see in Civ 7. That being said I hope to god they do not create a map generator where cliffs apparently form a part of the terrain every 100 or so meters. Humankind implemented this TERRIBLY, but regardless it showed it was possible. Civilization I just hope adds it, and maybe makes it more subtle. I would like to also say that I hope to god Civ 7 does not look to do anything like the garbage river system in Humankind (HOW DOES A RIVER BLOCK MY SIGHT!???). Something about rivers in Humankind feel bad.
-Civics. Again a very interesting system implemented very poorly which I think Civilization can improve on. On meeting certain criteria in Humankind (which they wont tell you) you are given a choice between two key options; for example when it comes to land rights you can choose between inherited lands or communal lands (can't remember what it was exactly). These each have an effect, but in addition to that effect they impact the affinities your society takes on.
These affinities include things like Individualism or Collectivism as an example (gold buff vs production buff). The main problem with this is that it never gives you information on how to attain these Civics, so they feel very random. The other big problem is it mostly translates into yield changes. Leave an affinity in the centre? Gain Stability. Lean towards one of the affinities, and you gain a buff to a yield like bonus Science vs Faith, bonus Gold vs Production, bonus Influence vs Vision, bonus Strength vs I cant remember.
I really hope Civilization attempts to look at this system but really push it to having more impact in place of yield buffs (which are always extremely boring). Go Collectivist? Natural Trade Flow shifts away from your Empire, you leak less Science, and Spies have a much harder time infiltrating. Go Individualist? Natural Trade Flow shifts towards your Empire, you lose a small percentage of your Industry to gold production, and Spies are much more easily able to infiltrate your society. Some of these should have disadvantages associated with them if you are playing an empire where a certain affinity makes no sense (going Collectivist and yet every city has market squares, you are openly trading with several other civs. etc. should come with some unhappiness, afterall you've modeled your empire in such a way that individualism would be sought after by the populace).
Again not a dev, just some ideas on how you can avoid it being a boring 'gain x% more of Yield'. Obviously, do so with the information in place as to what criteria triggers the events influencing your society.
-Neolithic Era. Once more a great idea, implemented poorly! In Humankind the system works by seeing you play as a tribe running around picking up anomalies. These anomalies are either representative of knowledge pushing the tribe towards understanding how to settle as a civilization, or food increasing the size of your tribe. When you gain enough tribe members or learn enough from the knowledge curiousities (or hunt down a certain number of animals) you gain the ability to progress to the next era. The problem here is two parts:
a - The system created is VERY abusable and the bots have no clue how good it is to stick around in Neolithic. Players can grow the size of their tribe to essentially immediately build a huge army of scouts.
b - The nomadic element feels like a great way to continue on as Civilizations like the Huns, but no matter how you played in the Neolithic era you are more or less the same as every other civilization. In fact weirdly enough you might settle into an immediately huge sprawling empire assuming you nab enough influence whilst in the Nomadic phase.
That being said, it alleviates an issue Civilization has always had to deal with; poor or boring start locations.
I would really hope Civilization looks into adding a pre-civilization era. Hopefully implemented in such a way that you can't abuse it, and where it impacts the future of your Civ, potentially retaining a Nomadic mode to continue on into future eras (maybe a system where they have 3 or so tech trees that you can opt to go into (Tribal Confederency, Nomadic Horde, Cities), with the tech tree defining the mode in which your civilization exists, with each having a method to transition into the main tech tree (Cities)). Such a system would likely mean that you wouldn't choose a Civilization until you complete the Neolithic stage of the game, just like in Humankind, as Civs would be locked to different tech trees, but it allows the system Humankind devised to be used to model alternative civilization styles, and it allows players to make much more sense of playing Civs like the Mongols or the Cree.
-Buying Wonders with Influence. I suspect some people see the system implemented in Civ as part of the strategy, but I don't think it is EVER enjoyable to be 1 turn away from finishing a wonder only to have it yanked away by another Civ. I would personally like to see some kind of resource that you buy wonders with, though they would have to be careful with all the buying resources, with Great People Points and Wonder Points. Maybe it'd be interesting to see them as a single unified resource used to buy your Great People and Wonders. No clue how they could approach this.
I will say that I really hope Wonders in Civ 7 are not as boring as they are in Humankind. My god are they terrible... Especially Natural Wonders.
What I would not want from Humankind:
-Changing Cultures. I really think this is something everyone else wants, but I feel like Civilization needs to retain its identity as that game where you play against a Ghandi whose Nuke crazy. The Immortal Leader is a part of the Civilization Identity, and I don't think that should change. Just a person opinion on this one. If they went the other direction thats not a 'not buying it' thing for me though. It is worth mentioning that I feel like the result in Humankind was rotating between never interesting civilizations; I would much rather see exciting Civilizations that you are stuck with, although I do dislike how gameplay defining each civ can be in Civ 6, where their perks really push you in a specific direction. Its a weird balance that I am sure the devs have a hard time trying to figure out.
-A non-informative UI and bug riddled game that focuses on shiny. Please don't.
-Turn Based Combat in a Turn Based Game. Honestly if I had a choice to see where Civ could learn a thing or two about creating an exciting combat system I would love to see a 4x game take a look at what HOI does, where you develop your units into armies and position them in lines, where the lines naturally engage one another. Sort of like a simultaneous turned combat system that sees the player focus on positioning and forming their armies correctly. But thats a SUPER wishlisty thing.
The combat system in Humankind is poor for two reasons; the impact of terrain is too favourable for the attacker, having a system where you are just waiting for armies to be positioned in the right way, I feel like it'd be even more abusable in MP; the bots are TERRIBLE at taking advantage of space or even understanding the strengths of their units. If Civ has a history of one repeated achievement, it is repeatedly poor bots, so I don't think they should implement systems where bots need to be particularly competent.
^I am personally thinking about things from a gameplay first point of view. The historical accuracy of the game doesn't matter to me as much. Apologies if its not well articulated.