I don't think this is a little thing, but it also doesn't fit the other threads we have underway regarding Civ 7, so I'll put it here.
I wonder if the late game could be made more interesting if the rival civs 1) were better programmed to band together against you when they see you emerging as the clear leader in terms of some victory condition and 2) had specific resources for them (when working collectively) to impede your progress, but of course 3) there were things you could do in response to that drag that they put on your march toward victory.
I play Civ V, and in a small way, that's in the game, at least for Domination victory. As you start conquering, you get little indicators of their displeasure on their leader-screens, and then at some point a significant number of them will all declare war on you at once. That actually does represent a good mid-game challenge for me, because it often happens when my troops are spread thin, and I really do have to scramble to defend on other fronts. But it happens mostly just with regard to that victory condition. I'm thinking a little bit also about Civ V's ideology dynamic, where, once you've declared, the number of civs in the two other ideologies might have sufficient cultural pressure to make your happiness tank and set you back a little bit.
I think it would be cool if, for every victory condition, the other civs could band together to make it, in some practical way, more difficult to achieve that victory condition. Not that automatically the whole world gangs up on you, but just that alliances against you become more likely, and that those alliances can truly represent an impediment to your progress. You can ward it off a little through favorable diplomacy. You can just amp up even further the things that contribute to the victory condition you are pursuing, etc.
It seems like a manageable addition to the diplomacy AI (in Civ V the drag on happiness is nothing other than a function of the fact that you have two ideologies subtracting from your happiness and only one contributing to it, so with no more "brainpower" than that, the game can give you a little late game challenge). Anyway, that there be more such resources for rival civs in alliance to impede your progress, though in every case with something you can do to combat, or pre-combat by good empire-management, that resistance.