IRC is a good parallel, on large networks you can create, join and get banned from thousands of channels, but you're still on the same network with everybody. You can even get banned from individual IRC servers on the network and still carry on as if nothing happened, because all servers on the network share the same data. Similarly, if one of the IRC servers on the network disappears and never comes back, no channels on the network are affected.

What you are proposing is similar to the hundreds of single-server IRC networks that have the one large channel run by the same people who run the server itself. If you get banned, you've lost access to the channel and all people on that IRC network. You now have to join another one and hope that you can find some of them there. Similarly, if the server gets canned one day, your channel is gone with it.

Your argument is you could run your own IRC server and people could join that. What I'm saying is we shouldn't have to, it's easier and better for Nostr to keep relays generic and solution for communities at a client level, similar in concept to the large IRC networks in this example.