This thread kind of confuses me. There's a whole lot of talk about nerfing walls, but I don't understand how this will make the game any challenging or better. In fact, it will make it much, much easier as any hit to the AI's defensive's strength will make stamping them even easier than it already is. To the various people who say warfare "grinds to a halt" after walls go up: with great respect, I don't believe you're doing it right. Beating walls is very possible, you just need to plan properly. First, great generals are absolutely mandatory, which is how it should be for a domination game. They allow your siege to fire the same turn they move, including moving onto a hill for better line of site. Getting in a couple shots before the city has time to respond makes all the difference. Second, you need to plan the whole thing out. Don't move in your units willy-nilly like the AI does, arrange it so that 2-3 siege units are moving in and firing on the same turn. Third, make use of siege support units. Battering rams won't stay good long, but siege towers are often useful for quite some time, and can let 2/3 upgraded swordsmen/musketmen make short work of a city. In a good domination game (Deity only, natch) I'll only use air units to take maybe the last civ, or often not at all.
No, I think walls are fine. I much prefer the suggestion I saw earlier to just give the AI (but not the player) a flat +25 CS boost against districts. That would let AIs have an easier time conquering each other, as well as being more threatening to the player, without making them a joke which removing or heavily nerfing walls would absolutely do. Walls aren't here to protect us from the AI, they're here to protect the AI from us.
I will assume that you are talking about Deity here, and assuming that we're talking about a regular start here (no ridiculous tile yields or other immediate strong advantages, no very flat lands with few forests/rainforests, and not playing something OP like Byzantium/Gran Colombia/Sumeria, abusing broken mechanics from the new NFP modes, or otherwise restarting the game until you get a desired good position to play from).
Based on these assumptions, I respectfully disagree with this.
In some games, you are forced to go on the offensive early as you're quickly getting boxed in.
Especially when your neighbour is going heavy on tech (which these days is more common than not), you are left with only one good option to break out of the encirclement and get the ball rolling - an Ancient Era rush.
In such a scenario, you need to be very quick about getting enough warriors and archers out to conquer at least one city, before the enemy gets walls up.
This window is so short on Deity that you don't have time to build encampments, as you need to get a base of 2-3 cities up and spam units from those.
You will also not reach the Battering Ram/Catapult techs before the AI has produced said walls, leaving your units in a position where they are unable to take down the walled city.
Failing such a rush is more or less a lost game, since the AI is snowballing ahead while you usually can't catch up from there on anymore.
For instance, I remember one game where I tried to do a delayed rush with Alexander against Korea (foregoing the Warrior/Archer rush), in favour of rushing Hetairoi and Hypaspists with Rams/Siege Towers built off of Encampments and Campuses until I had the unit tech for Hetairoi/Hypaspist.
Even though I had planned out the rush as good as I could, Korea was snowballing so hard that she had Coursers, Crossbowmen (and a bit later) Knights(!), as well as walls out by the time my units arrived (including about triple my science per turn at that point).
Needless to say, Battering rams/Siege towers did not cut it against such resistance.
Heck, I've even played around with some restarts to test out the difference between walls and no walls, and a rush that failed and lost me one game (because walls came up in the last moment), would be a similarly easily won game if I could shave off 1 more turn before the walls went up and conquered said city.
The next game for instance I played as Alexander and again spawned near Korea, but this time I Ancient era warrior/archer rushed her before her walls came up, and got her crippled down enough to break her with delayed Hetairoi/Hypaspists (foregoing Encampments completely in favour of more Ancient era units).
The bottom line here is, you cannot wait for too long in order to attack the AI, otherwise you can find yourself completely boxed in and unable to catch up to an out of control snowballing AI.
Other than that, yes I can and do win frequent domination games on Deity (my last 2 games were domination), but the Ancient Walls are too much of a game changer on Deity.
In the Ancient Era/Classical Era, you are still falling further behind on tech and production compared to the AI, and you need to do something about it before that lead gets too big.
Ancient Walls are just too much of a crutch for the AI, and it doesn't help that they get said walls up before you get the tools to deal with them (they do have a tech lead after all), and by then the game can be lost if you're boxed in without the tools to break out.
As for "moving in units simultaneously" to get early shots off (and the city sieged), that's basic knowledge which I always use.
But let me be clear on this - this advice doesn't always work.
If you face off against a city placed in Rainforest/Forests and lots of hills (which does happen regularly), you can't shoot from an elevated position and sometimes have to move Catapults right next to the city to even get a shot off, which by the time you do get there, has cost you 2 turns where the defender could freely shoot/attack back at you, and this too frequently often costs you so much that you can't keep your army up before it gets chopped down.
As for an extra combat bonus for the AI against walls, I'm against it.
Civ 5 proved that you don't need the crutch that is civ 6 walls, and still not have it "too easy" when going Domination.
Add in a baseline ranged strike for all cities irrespective of walls (like civ 5), and have walls give extra hp and combat strength, but no hidden combat strength modifiers vs melee units (again like civ 5).