It's not only the "base" instance IMO, most servers have wildly different communities.

There should IMO be some way to search for communitues from any server (and subscribe to them, which is a real hassle especially if your base server doesn't yet know about them). I like the endless flow of memes as much as the next person, but what I really want is a bunch of communities I'm interested in so that I can lurk, ask questions and eventually create some hi quality content.