I also hate diplomatic AI. They are jerks for no reason and often don't want to accept trades that are VERY good for them, like their 1 surplus luxury for three mine
. It's just not very smart. Also its funny to be called warmonger or such by Iroquois who pretty much conquered half of large continent while only thing I ever did was conquering 1 city state and I did it because 2 other neighbouring city states asked me to do it. Also AI is too war happy. They declare wars left and right without any kind of plan, very often all I ever see is 1 scout unit that quickly dies, several turns later I get asked for peace treaty, sometimes I get really nice extras for no real reason (my units never moved out of my borders).
I encountered bug like this. I got city for signing peace treaty after Washington's army suicided on my defences. I make puppet out of it and then I can't hit next turn because I have to select production in New York, of course I can't, I could assimilate it but I don't want to, had to reload.
Also pro tip: if much larger nation wants to sign research treaty with you, you can be pretty much sure they will attack you the moment it's finalized. It's sound tactic, I get research and whoop their ass anyway so no gain for them but it's too obvious if it happens so often. I noticed I get attacked much less if I don't sign such treaties with super powers so it looks like its exploitable by human players.
AI isn't horrible but it needs a lot of tweaks.
Oh there is one another thing that bugs me. Research, best way to do it is to conquer huge amount of cities. Smaller nations have hard time catching up. I liked how it was done in EUIII. More realistic in my opinion, let's look at actual history,
relatively small countries like Great Britain or Spain grew to be global super powers thanks to advanced technology. Hopefully someone will mod it in.