I think the future of online communities will be community for the sake of community…and nothing else. Very mundane and boring on the outside, driven by nothing other than “I’m sharing waffle recipes and I’m going to just upload them to the internet on my hosting provider or via my old Compaq Presario and I do not care about engagements just email me later and goodbye.”
Hell, it's only about 45 million in the US (assuming you believe Twitter's own numbers - which I definitely do not).
So at best, you're getting 1 in ~8 folks in the US. More realistically, I'd assume your audience is more likely 1 in ~20 in the US - assuming you manage to get literally everyone to follow you.
Is that larger than you're going to get on your own site? Probably.
Is that everyone? fuck no. It's basically no one. You're reaching the worst 5% of the country - those who have nothing better to do than browse twitter, or those who are using twitter to promote themselves.
The brief exception to this is politics - where Twitter was an easy way to get a relevant soundbite from a politician on a topic. I think that era is waning very quickly.
Most media sources aren't embedded in small forums.
Admittedly - it's fairly certain that some of those will be about ycombinator itself - but I don't really find that outside the scope of the ask - given that many of the hits for twitter are really just following the company drama and not expanding the reach of a single user's tweet.
Not true; you can build and own your own "island" and grow the population of your "island" to be quite large. This can and does happen quite regularly. It's the only sensible thing to do, really, if you want to build a sustainable platform.