These things already exist and struggle exactly because people comfortable with the walled garden approach forgot what FB was like in 2006 when you only knew 15 people on there. The lack of critical mass of your personal contacts outside of the walls is exactly how FB and IG keep you from venturing outside the walls.
Friendica is one of several fediverse platforms the author basically describes. You can even self-host an instance for yourself and friends/family.
And you may say:
> I tried Mastodon once, which is not immediately intuitive, and the apps aren't perfect. Plus, the wikipedia article describes something that isn't perfect, so I shouldn't bother.
Perfect. IMO, the minuscule friction to enter is the benefit. The walled gardens exist and hold people in such high numbers exactly because they've reduced the friction to enter and increased it to leave. The definition of a trap, yes?