The point is your instance doesn’t automatically pull every community in existence, it pulls from communities someone on your instance has already ubscribed to. So yes, you can subscribe to any community*, but you may need to be the first to actually find said community and subscribe no one else has.
When I browse my all feed I see posts from every community that anyone has ever subscribed to on my instance. But if I find one I like elsewhere I can be the first to manually connect (copy paste link) then more people can discover it since I basically added it to their “all” feed too.
Less confusing than I made it sound, and as the user base grows most of the big interesting communities will have been found and federated on instances with decent userbases.
The point is your instance doesn’t automatically pull every community in existence, it pulls from communities someone on your instance has already ubscribed to. So yes, you can subscribe to any community*, but you may need to be the first to actually find said community and subscribe no one else has.
When I browse my all feed I see posts from every community that anyone has ever subscribed to on my instance. But if I find one I like elsewhere I can be the first to manually connect (copy paste link) then more people can discover it since I basically added it to their “all” feed too.
Less confusing than I made it sound, and as the user base grows most of the big interesting communities will have been found and federated on instances with decent userbases.