Civ 6 needs an expansion or two to really make it great. I love it and the new mechanics are fun, but the AI isn't so great and the game just needs some more fleshing out and polishing.
Civ 5 complete is superior but I can't go back to it because the new mechanics of Civ 6 are really good.
AI is truly 2K's weakness, I bought XCOM2 and rage quitted (refund) after an hour... and I played tons with the 'orginial' Enemy Unknown/Within...
I just play stellaris
I was toying with buying it, but with kids and Elite next to it, I'd never make to learn that game.