Virtually everything put me off.
1. Uninteresting Clash of Clans type art. 2. A selection of leaders that make no sense except to appeal to hyper political people who don't even know what the game is. 3. Asian leaders not looking like actual Asian people even remotely. 4. Lack of good mods. 5. Terrible city system where buildings now hog up huge swaths of the map (have fun trying to be Korea on a real world map). 6. Civs that should've been in the game by now not getting a chance again (Ancient Israel, Tibet). 7. "Diverse" units only being slight costume and weapon changes to units instead of using their imaginations to theorize what they would have looked like if nations developed these things independently. 8. Those changes only running up to early Renaissance units and not through to the present day units. 9. Little sense of the epic scale of time and technological advancement as in previous games. 10. No interesting scenarios, or scenarios that have been done better before in the past.
Overall, it just sucks. Civ IV has issues, but with its highly versatile modding abilities, you can fix nearly everything. It also has close to two decades worth of content that can be added in now, and while it is still in need of proper city sets for other nations (which I've made but have no idea how to texture or rig), it's still much more interesting than Civ VI's boring cities. I love how in Civ V they actually bothered to make different city sets up to the present day for the major culture groups, which makes it more exciting and like you're doing what the game advertises, rewriting history. But in Civ 6? Nope. Don't even bother to make the modern stuff different, Conform it all, like in real life, despite that I'm literally changing history from the ground up.
I get it. Israel and Tibet are controversial. I don't care. Stop capitulating to foreign markets and their ridiculous contempt for these groups. People surely hated the Mongols too in Medieval times, yet here they are in the game. They, like Israel and Tibet, still contributed to history as civilizations.