In general I try to go in groups of 4, due to the amenities, but I definitely end up with 13+. Unfortunately, there's really no downside to wide play. I like it this way, BUT it should be a bit more of a challenge to pull it off. Amenities should be more of an issue, especially in foreign continent cities, GA penalties harsher, conquered cities harder to please, etc.
FULLY agree. I love wide expansionism but Civ6 doesn't punish it enough. In Civ5 you get scaling tech/policy costs (too much actually but VP fixes it). Rome Total War has civil wars and such.
If they ever do a third expansion I really hope they put in some corruption/revolution mechanics that make wide empire management more critical.