Patreon, Substack, etc have benefits in discovery. Self hosting requires that you figure out how to get discovered. That’s the main problem here.
… which means it’s a problem.
There are lots of options for running your own Mastodon/ ActivityPub implementation, etc—it’s not easy, though. This is purely a technical problem.
Of course, I am not really talking about Chirp clones here, but this is a pretty good analogue for comparison.