A large popular platform can be a safer, more diverse & more welcoming space.
I strongly dislike the tendency of people to abscond off into private communities. I don't like places that are not public & open. Mostly facebook groups convinced me that such places can be the most toxic places possible online.
I want a big public square and the intersections that such a place makes possible. I don't just want to talk to math people and tech people. I hate the isolation.