I think that's because it's a hard to grow a new community. I don't think that makes it invalid. The primary reason people look for a new platform seems to be because their behavior wasn't accepted on more mainstream platforms.

Lemmy has some content problems, but I haven't ever noticed it nearly as bad. Mastodon is somewhere in between, but at least there's some good stuff there. Threads is definitely the chillest microblog platform but feels a bit too artificial at times. I would personally take Twitter, even at its current state, over Blue Sky all day long.