Enemy + ally AI sitting on 20000g and...

[Makavcio]

It's a problem that popped up with GnK. In vanilla, mercantile AI was always able to bribe all city states in the world making your life miserable. Before spies and complicated missions, it was the only way to accomplish anything with city states and AI was always willing to use it. Since GnK they totally don't care. It's a grievous bug that hasn't been fixed yet. I understand that not all civs must always go for each and every city state but when there is an "infrastructure project in progress", AI should be able to use 2-3k gold (10% of their savings) to secure its domination.

 

[OmniPotent42]

The problem is obviously that if they would use their immense gold stacks to do that, you would never again be able to win diplomacy ever through peaceful means.

No, not really. With the right civs and trade routes you can outclass even runaway immortal AI in GPT, and if you really want them to hurt, embargo them or impose a standing army tax and watch their GPT drop into the negatives.

In my game Arabia was really good about spending his gold - he was always the WC leader because of it and for the first part of the WC had more votes than the rest of us combined. I think the reason for his spending was because he was actively pursuing a diplo victory, though.

 

[kaspergm]

I don't think anybody wants Civs to use their entire treasury reserve to win over a City State just to prevent the player from winning, but they should at least put up a reasonable fight for them, especially City States which actually have value to them as allies due to their bonuses or close proximity.

I want that! I want that!

Yeah, I would probably also want something like that, and/or some change in how diplomatic victory works.

I don't think that AI should auto-DOW you just because you are close to winning, that would both be boring and would not help them in this case, because a DoW to you would just mean they can't buy any of your City States. Instead, as KrikkitTwo said, they should evaluate what they can do to counter your current strategy. If you are close to winning Diplomacy, they should try to secure enough City States that you can't win if they have the money for it.