CIV 6. It's really hard to explain how uncomfortable I was playing that game. The cartoony designs (which are said to be the normal look in Civ) just makes me chuckle when a Civ with an oversized head declares war on me. The UI is fine, but it takes a lot of getting used to. The AI feels underdeveloped, and the result is that it makes them stupid. And most important of all is that the World Congress feature wasn't there. I used to enjoy forcing an embargo on a Civ and then crushing him when he can't retaliate.
Overall, I feel like the CIV 6 they released was a "prototype". But this has a silver lining to it: if Firaxis is responsive enough, all these issues are going to be fixed, and a lot more features are going to be added. CIV 6 can only get better from here.