You don’t have to make your own server (unless you really want to!). Just start a community on a server you like.

The one catch is that others can start a community of the same name and/or interest on another server and that gets a little confusing because then there are two, of course.

I wish that communities could “federate” with each other from different instances but then that raises a bunch of logistics issues about how this is moderated, how is this presented to the users, etc.