You say that but tfp has many times removed or nerfed something specifically to counter players, for example the sleeper trigger system was put in in a17 to specifically screw over stealth build players. Players that run and gun aren't effected by this system at all, it was targeted specifically to screw over stealth builds, then you have a22.1 aka 1.1, where they messed with stealth again as they realized the tier 6 assassin set bonus was way to strong. That set in 1.0 basically makes stealth somewhat viable, where as its basically not viable without it. Yeah yeah supposedly if your stealth is high enough you can avoid triggering the trigger blocks, but from experience i've never seen it work like that even with stealth skills maxxed. Haven't played 1.1 vanilla though yet, this is based on 1.0 stealth. Dunno if I'll bother with it in 1.1, vanilla just puts me to sleep to play it as its so damn boring compared to mods.
People used to like making underground bases and bunkers, oh look, tfp now has zombies that dig, removing that option from the players as well.
Next you have the screamer change in 1.0, they now spawn at 25% heat, instead of 100% heat, so now Run n Gun builds have a hard counter since you'll get a screamer after about 20 shots fired. Before you could clear a poi at least without them, but now? clearing a t3 poi is prob going to cause at least 2-3 screamer spawns during it. Again, this was done specifically to screw over/counter a certain playstyle
Need I go on? there is 2-3 concrete examples you cannot really argue against. Both being directly to counter a certain playstyle cuz tfp don't like it and had a hissy fit over players using it.
They are changes that were made, yes. That those changes were made to 'screw over certain play styles' is a claim I don't really see any evidence for.
The sleeper trigger system, I would strongly suggest, is only in the game because of performance. If consoles could constantly run AI for 100 zombies without breaking a sweat, while also running complex listening for noise calculations for each of those zombies so they don't start smashing things before they can reach the player, I'd bet a fair whack the trigger system wouldn't exist in its current form. I see the messing around with stealth, and the entire creation of the assassin armour, being an attempt to keep stealth viable when the 'oh so very necessary for performance' trigger system screws stealth over so badly. The subsequent nerf to assassin armour was a perfectly reasonable balance pass - tier 6 assassin was too good when it was released. You could crouch and machete a zombie bear to death over numerous swings in broad daylight, and it couldn't find you despite you being basically embedded in the bear's intestines.
Digging zombies doesn't 'remove the option to make underground bases'. It removes the ability to make absolutely safe bases that zombies cannot reach with two minutes work using a stone shovel and a wooden hatch. Anything that makes the player totally safe goes against TFP design intent. That they have stated on more than one occasion. You can still build an underground base just fine, but it doesn't mean zombies just cease to exist for you.
The screamer changes, I would suggest, were made to add 'randomness and danger to the world'. Again, trying basically make up for performance constraints, which, in my opinion, is what TFP are constantly fighting against and kludging around. I think both they and most players really want terrifying tides of zombies all over the place, but that's not compatible with having a game that will run on consoles and lower end PCs. Hence work arounds that only allow zombies to start burning resources when they're actively engaged with a player. Triggers, screamers, they're techniques for making sure all your active zombies are right on top of a player, not wandering around somewhere burning up CPU resource.
Sure, they chose to support almost obsolete PC specs and consoles. They could have said 'we'll build this to run well on what we predict is an above average gamer rig in three years time and screw the console market, they're all lamers' and I think the game would be light years better for it, but that would also probably be commercial suicide and they're a business at the end of the day.
The AI rewrite in A17 was specifically the example being made. Watering it down since then hasn't really changed the basic model.
Again, the problem isn't a specific AI model, it's that there is only one model. You know how many blocks they will rage at, you know what they'll path to, and so on. And those were changes made in response to zombies being too "dumb" earlier on, but the thing was that the supposedly-dumb zombies were actually less predictable.
There is the explanation wandering around that current AI is actually testing out rudimentary bandit AI, and they're a lot smarter than they should be, but I don't know if that came from an official source. Even if it did, that viewpoint may have gone by the wayside.
I'm really hopeful when bandits come in, zombies get stupid again, at least some of them do, but I'm not holding my breath. You're quite right when you say if there's only one model you know what they're going to do. Even if it was one AI model per zombie type, Moes just break nearest, Arlenes aim for weak spots, Spiders attempt to gain elevation and jump etc. it would add a hell of a lot of factors to consider to base design.