Weirdly, people don't have as many friends as they used to. That's why TikTok beat Facebook. Facebook is useless if you don't have a friend-graph IRL, like a telephone system with only one telephone. I think the future of social is going to be 1-on-1 interactions, everything else just becomes rep-farming, crowd-pleasing, performance art, trolling, etc.

Who even uses 3D spaces besides gaming? User-generated content is usually terrible, like Mario-maker -- most user-gen levels aren't any fun.

Anyway, go play SecondLife for awhile before you spend too many more cycles thinking about this.