I think there have been some areas of modest improvement in the AI, but if AI is a deal-killer for you, then you should pass on Gathering Storm for now. I’d give the devs (and modders) get a chance to adjust the AI to all the new systems. I would assume that most of the issues you mention will arise sooner or later.
That said, I personally haven’t seen any of the issues you mentioned in my 200-turn game so far. Obviously my game is a tiny sample size of just one. No civ across the map has declared war on me. The one AI that did attack me had the same tech and more military than I did, and it had good reason to do so.
I still had no trouble fending off its attack, as I was able to rush-buy many units to gain superiority, but its tactics didn’t seem outrageously stupid to me. It just needed more firepower, and it didn’t forsee that I’d use my big stockpile of gold to catch up fast. The AI should account for the opponent’s deep pockets before deciding to wage war, and it doesn’t seem to do so.
The main AI issue I worry about is the new resource system. It took months before the devs managed to get the R&F AI to start upgrading units properly, and now they’ve just changed the strategic resource system pretty radically. I love the change itself – I think it’s great that one deposit of iron no longer means infinite swordsmen. You spend iron or horses or whatever per unit. But I gotta believe this will be hard for the AI. In my current game, my local adversaries have made the first couple upgrades; too early to tell whether that behavior will continue.
As for the AI capturing other AI cities: the AI went hog-wild conquering city-states in my R&F games. But I do worry that the AI will have more trouble in GS because city walls are now double strength or something. I haven’t seen much conquest of city-states in my games, and really no big civ wars at all. This may partly reflect the new diplomacy system, which seems to inhibit warmongering. I have seen a couple loyalty-flips, though.
I also didn’t see atrocious city-planning in R&F, and the trend has continued for me in GS. I captured a couple AI cities and the builds made sense to me. I’m sure there will be examples of stupid builds in a game this complex, though, especially as again there are new systems for the AI to contend with, like new districts. (Incidentally, I was unable to hold one of the cities I captured because of loyalty issues; the second remains in doubt.)
The lakes I’ve seen haven’t had any AI ships. I do worry that the new canal district may exacerbate this issue, though – will AIs build harbors on lakes assuming that later they’ll add canals?
The diplomatic AI seems less bad to me. (Notice I didn’t say “better,” lol.) The new diplomatic favor means that civs have incentive to stockpile favor and to seek it, which tends to mean they have incentive to make appealing trades, seek alliances, and maybe avoid unnecessary wars that indirectly cost them favor (by piling up grievances and creating the possibility of favor-costly Emergencies). In my current game, I’ve had good relations with all but the one AI that attacked me – and it had good reason, as I plopped my Maori down right next to it. That said, I do find it annoying that the AI constantly pesters me to sell it diplomatic favor or resources or whatnot. It would be nice to have a “do not disturb for 10 turns” button, lol.
I haven’t seen AI cities in the Arctic or other awful spots yet, but there’s still time in my game for this to happen. I did see this in R&F, which was disappointing because I would have thought the loyalty algorithms would’ve discouraged the AI from doing this. I’ll watch for it.
TLDR: no radical overhaul of AI here; my impression is that diplomatic AI is somewhat less annoying; but I worry about the impact of the new strategic-resource system.
