Between the release and the betas I've noticed that making alliances with almost everyone seems to be way too easy.

The only games where I ended up not being able to do it where two games where my religion got replaced by another, which kept generating grievances for the rest of the games. (and thanks to the Internet I now know how to change my state religion which would solve that issue entirely)

But other than that, the AI seems to be fairly quick to accept alliances and doesn't really care if you're already allied with their worst enemy.

Anyway, the diplomacy screens have been improved since the beta but the mechanic feels like it could be more challenging.

Close proximity should penalize alliances more (at least in the earlier eras) and, when two of your allies go to war with each other, it would be cool if they asked you to pick a side rather than just give you a grievance you can ignore.