Yeah, you want to stay away from this one, at least 1.0. The diplomatic AI is really bad, especially when you’re used to EU4. And I don’t mean bad as in it performs poorly, I mean that its completely nonsensical most of the times.
I’ve had similar things as Olaf where an AI asks me to join a joint war with him. I agree, only to have the AI hate me because I’m such a mean warmonger. I’ve also had Teddy Roosevelt, who is supposed to hate warmongers on his continent, tell me I had left him no choice and declare war on me, because two other civs (of different continents, at that) declared war on me while I was minding my business. He didn’t get mad at the foreigners attacking his continent, he got mad at the victim that he’s supposed to protect.
That’s not to mention the wars that serve no purpose. It’s the start of the game, there’s land aplenty for everyone to settle cities, yet Pedro of Brazil declares war on you right out the gates. Why do this? Put the resources towards a settler and expand, especially for a country like Brazil that is geared towards a Cultural victory? In the 30+ turns it takes them to march over to my city, I’ve built up defenses and easily fend them off. IMO, the AI should not be declaring war unless it is advantageous for it to do so, or at least in-character (Montezuma, for example).
It’s also got the age-old problem in the franchise of the AI suffering from multiple personality disorder. You’ll be best buds for centuries, declaring friendship, having lucrative trade routes with each other, and exchanging luxuries. Then I’m assuming the AI does a quick strength comparison or something and decides it might win a war, so it attacks only to have it’s inferior forces utterly annihilated.
A lot of people handwaive it off with a “it’s a board game!” but that just doesn’t hold water for me, a lot of these decisions are just poor decisions. And there’s no reason that Civs geared for Cultural victories and the like should be instigating wars with distant nations when they could be peacefully expanding and building wonders.
All in all, it’s a little frustrating that they lifted diplomatic concepts from EU4, like warmonger penalties and having a casus belli reducing those impacts. But none of it matters in the least with how randomly the AI behaves. In my experience, being a warmonger will cause civs to Denounce me, but they always attack me anyway so what does it really matter?