Sadly, a conclusion I'm leaning towards as well. In theory this system should allow an even greater mixing of ideas than Reddit and its ilk, there's no central authority determining which subjects are forbidden. But it seems we just do that to ourselves anyway, and since each instance and each community are so much smaller than Reddit it's much more effective. The same "single giant impersonal central authority" thing that's a downside of Reddit also means that it's easier to seamlessly encounter everything that is allowed under it.
I don't really know how to fix this since it seems like most people literally want it to be this way. We don't like having our views challenged, it's comforting to look around and see that everyone agree with you.
Well, this isn't limited to indoor spaces, then.