It's good that there's another Civ game in development, I played IV to death and have played VI a fair bit.
I actually like the districts in Civ VI, it forces you to plan ahead when placing your cities. What I don't like is that the military conquest option is so much more powerful than any other strategy. Once you start rolling and have captured a few cities your science, culture and money etc. start ramping up and you can eventually just steam roller all the other civs or switch to some other sort of victory half way through. Some sort of corruption penalty for having too many cities might help balance this, make a player choose which cities to keep, raise or give away.
It doesn't help that the AI is so dumb either, it will only attack if it has a much stronger military and this only happens in the early game. After this it never goes all out to build a bigger military than you or team up with another civ to beat you. An AI that can move groups of units tactically rather than sending them in piecemeal as at present would be a big improvement too.
Civ VI's religious unit spam is another really annoying feature, hoping they come up with something better in VII.