(So this also means a large percentage of the people now left in sneerclub will be the worst, so it might finally morph into the boogyman the Rationalists always made it out to be).
Some people seem to be genuinely happy it's back, but that could just be the honeymoon phase, so let's see. I might even post there now and then since I still use my Reddit account because I stuck around thanks to discoverability in the Fediverse being just awful which means I haven't found a good replacement for a bunch of communities I like.
I think the biggest problem is either the lack of active moderation or, if present, moderators which are too lenient. Not that I blame anyone who thinks that removing the fifteenth racist asshat for the day is not the best use of their time, but the best communities are the ones that to make the effort to keep it clean.
This has been true since the days of Usenet. The good groups were completely moderated to the point where some person had to manually approve every single posted article. It worked (as long as the mods weren't racist asshats themselves, which is a different problem), but in contrast, almost the entire alt. hierarchy was an unmoderated cesspit and to anyone who doesn't know how that turned out long-term: good for you.
Luckily I think we are seeing a rise in moderated communities again. After Usenet and dedicated forums it somehow fell out of fashion (with 4chan and Reddit being the pinnacle of using but muh free speech! to give bigots a platform). Maybe it's confirmation bias, but I do see many fedi instances who have stricter rules again and seem to enforce them in an attempt to create welcoming communities for everyone. I hope this trend continues.