We have ample evidence that platforms whose goal is to shove everyone you've ever met into the same room isn't a good thing. Modest growth and a healthy community that doesn't have to include everyone to succeed seems like a good thing.
Sure, but not if you've taken venture funding. We already have a public, community platform for building slow-growing tight-knit communities: Mastodon/ActivityPub.
It's not one platform. It's a set of independent platforms that sometimes federate. The M/AP federation experience is a third-class experience. Cool kids don't federate, they're already on the server with the people they talk to.