I can't argue against your experiences, but in my games so far, aggressive Civs being aggressive and peaceful Civs being peaceful is exactly what I've found. What I have noticed is that the AI is much better at winning the game peacefully without needing to recourse to war. I really haven't noticed any indication of any problems, much less it being 'broken'.
Pre-BNW, your nearest AI neighbour - regardless of who they were - would attack you early game. Almost every time. I have around 1,800 hours' worth of games and over 90% of the time this was the case. It was just How The Game Worked. I found it tiresome and predictable. Now that still happens sometimes, but not always. Which makes the game more variable, more difficult to anticipate, and more fun. Instead I'm facing challenges in terms of other Civs' expansion, City-State influence, aggressive religion, tech rates, Wonder races... and yes, still war, but the AI doesn't rely on conquest the way that it used to.
But as I say, I'm all for making aggression levels customisable, and the likes of Attila, Augustus, etc. should attack early. Just don't force everyone to go back to the pre-BNW 'oh look, I've started within 12 tiles of Gandhi's capital, TIME FOR WAR!' charade.