From some of the things that are getting said in this thread and other threads, I'm starting to get the feeling that a large problem people are having with districts in general is that they don't do what players want them to do, or what players expect them to, or don't do it well enough for it to be worthwhile for players.
A solution MIGHT be to have government policies that can help improve these things in various ways. Civ 5 had this a bit, certain social policies or religious beliefs could be quite strong, but specialized you. The vox populi mod for Civ 5, which is one of my favourite mods by leagues, did this a lot more. The result is a fun and interesting game. There is tons of replayability because the way you achieve what you want can be different each time. If I had to visualize gameplay in this style, it would be snake-like or like a lightning bolt. Civ 6 gameplay is very different. It feels more like a straight line, with small shoots reaching out to take various things.
The devs said they wanted to do away with the build order for techs that Civ 5 had, and I believe they did this to a degree, but other aspects of the game seem to lock you in even more than in 5.
To be honest, it's been quite a while since I've played an actual game of Civ 5, and I never won single player above emperor. Most of my memories are of playing Vox Populi and that was an entirely different experience.
In civ 5, decisions about your government were permanent and could not be changed. Religion could be a useful tool even if you weren't trying for religious domination (which wasn't a victory condition), whereas in Civ 6 religion seems very bland and uninteresting.
Finally, what I think Civ 6 should do to fix this is add new types of policy slots and cards to governments. As things stand, we have military policies, economic policies and diplomatic policies. The function of each type of policy is only loosely defined. For example, one would expect military policies to be useful for combat, military expansion and producing units. In reality, military policies do do this, to a degree. For the most part though, military policies are some variant on "increase production towards X type of unit from Y era by Z%".
Economic policies meanwhile seem to cover every yield in the game: food, gold, production, science, faith, culture, tourism, district adjacencies, amenities, and housing.
Finally, Diplomatic policies can increase yields but are generally focused on spies, city states and allies.
[Ignoring wildcard policies for a moment]
In my opinion, this puts way too much pressure on economic policy slots. They've crammed so much into the economic policy cards that you're forced to only use the objectively best policies. There could be a lot of room for interesting strategies through use of policy slots but most of the time, players are prevented from doing so because they'd be giving up something more important.
So I say add more types of policy slot. Diversify economic policies into cultural policies, science policies and economic policies.
I think there's more than enough merit for this. It increases the number of policy slots available at each era but there's nothing wrong with that. Cultural policy slots can cover your government's opinion on domestic culture. Through different eras, this can encompass different types of yields, for example in early eras, maybe your civ's culture is based around their religion (as many ancient civilizations were; their religions having a major impact on every part of their life). They have festivals and rituals honoring their faith and this provides culture, so this policy might be that religious buildings also produce an equal amount of culture as faith.
In later eras, maybe culture is related to trade and economy, your people's culture flourishes through art and cultural exchange all over the continent. Maybe your culture has diversified and flourished in the small towns that dot your vast empire, and that diversity makes you stronger? Later, your culture builds from media centres and museums and art galleries, it also impacts tourism and amenities.
Science begins as philosophy, your government endorses the natural sciences and encourages your people. Perhaps early science policies split their yields between culture or faith, as many early scholars were monks or poets or writers. Maybe you get science from exploration, or from each new civ or natural wonder you meet. Later, your science builds from scribes and more specialized learners or from apprenticeships and guilds that work to specialize the crafts, skills and trades, refining the understanding of each field. In the modern era, maybe you have state sponsored education, allowing you to trade gold per turn for science per turn, if your economy can support it.
There are all sorts of interesting and nuanced ways to handle governments that would allow civs and players to tailor each game based on the victory condition they are going for or even the way they've played the game. Certain policies may be better if you happen to have a lot of mountains or forests or jungles, etc.
If players had more ways to customize their game, districts like the Entertainment Complex and Holy Site could be enhanced to perform better in the game.
EDIT: There's a lot of room for interesting policies that could change the way you play the game. The only problem is there isn't any room to add them in a way that players will actually have the opportunity to use them. Imagine a policy that gave near instant travel for units along roads in your territory at the cost of gold per turn maintenance on road tiles. This is essentially a government-sponsored highway and could have many interesting uses as it makes roads much more useful by allowing very quick travel around your empire. There aren't many policies that do more than slightly change a few numbers like adding or decreasing a % onto something. Few policies do something like change the way you can play the game.
