That only works for about seven years at a time, though. Eventually, the app where your college-aged college friends are (Facebook) becomes the app where the adult-aged friends you know
from college are (Facebook), becomes the app that the next generation thinks of as "the app their parents use", and therefore don't want to post anything public to lest some adult who knows their parents sees it.
So far, I'm pretty happy with the "isolated communities with shared identities" model of Slack/Discord. I feel like something that took that model and made it into a social network would be popular. (No, not like Reddit. Picture, say, Tumblr, but you can't reblog something if it's not from your community, instead only being able to create your own original link-post to it that doesn't propagate its interactions back to the community of the post it links to. So you have one shared piece of Original Content, but each community has its own sandboxed graph of likes and shares and comments and other interactions built around that Original Content.)
