Diplomacy, it failed really horribly, in my opinion.
Military, although it was an accepted update, the A.I. didn't seem to know what to do with it in my game.
Religion, very critical to me, the lacking of stripped me of my main strategy. The game just felt naked.
Civics, where'd they go? I wondered. Governments in reality are subject to change, which in the Civ world it adds greatly to strategy.
City States, was supposed to be AWESOME to me. A small country you befriend finally(I enjoy weak allies)! Oh, uh, oops, false alarm, the relationship with City States dwindles too rapidly to reap full benefits. It's like paying somebody to be your friend..
THE ENDING, the part where you watch your whole country go from start to end along with the other civs. Missing in action. That's a really brutal blow. It's like they're saying "alright thanks for playing, bye...that's it, go away now". It's a vital part of the game for me (as I play on Epic and Marathon mode).
UGH, it could've been so much better.