I'm not sure about overall activity, but I do know my feed is active enough that i can't read ALL of it unless I spend like an hour or more per day on here, and that's plenty active for me.
MxRemy
I migrated to the flagship PieFed instance a while ago and haven't regretted it at all. This place rocks! I would love it if there was an app though, not a big fan of PWAs lol. If I was smarter, I'd try to make one myself. Very exciting to see more instances popping up!
I assumed, by "They are not being as used as I expected/hoped.", that the OP was implying, "- by the members of said instances". And that the closed-registration bit was part of the proposal, not the existing state of affairs. I didn't realize their instances were already closed-registration.
Ah, I see. I misread a bit. I thought they were being used differently than expected, not less than expected.
I don't run any instances, but that does seem potentially like a pretty neat idea.
I am really curious about the unexpected behaviors of your instance members though! What are they doing, just treating it as a general instance and not really engaging with the local theme?
Mirlo.space is working on federation too. I think they're not as far along in that regard, but further along in terms of being a bandcamp replacement? Last I heard, anyway. I buy stuff from there, payment works.
I can't say that the ability to follow individual people is really something I care about, but coming from Piefed, it does seem to work just fine. So does Peertube and any of the other ones I've bothered to try.
That's where I'm at, nice place!