Personally I think "lemmings" is great because it feels slightly ironically funny and mildly self-deprecating but not in a bad way. Like, the stereotype of lemmings, even though it isn't really true, is that they're blind followers, which doesn't at all fit the fediverse given it's decentralized nature and lack of one singular direction. Meanwhile, calling some group of people lemmings feels slightly derogatory, but calling oneself something like that gives the feeling of not taking oneself too seriously.
Yeah I've seen people calling others here lemmings, it's a funny name but if you think about it, here is part of the fediverse and with that comes the thing that it isn't just Lemmy, there are other platforms (like Kbin) involved, so i think that a more universal naming would probably be more fitting