Part of Pawoo's problem is that it has been defederated and blacklisted a lot because of the early prevalence of lolicon and shotacon content on it: I'm pretty sure Pawoo was originally the reason why Mastodon added the ability to block media proxying to a given instance. Misskey for some reason hasn't really experienced as much backlash despite as far as I know having similarly relaxed content restrictions.

I don't really know exactly what makes Misskey more popular now: I doubt Japanese users are that concerned about the content moderation on Pawoo, though I could be wrong. It may help that Misskey was developed by a Japanese developer and is prevalently Japanese-first.

Misskey does have some neat features, though personally I find the interface to be dizzying and very busy.

I'm not referring to lolicon or shotacon, most of fedi has a chip on their shoulder even about much less controversial things (see: preemptively defederating threads.net) while it's far less of an issue in japanese artist communities - pixiv for example, gets by fine with it as long as it follows japanese laws.

I'm referring to creeps announcing in their bios that they're into real children (with them emphasizing the "real" part) and talking about what they want to do with them.

My japanese isn't good enough to tell if the situation with that sort of thing is bad on Misskey.io, but with Pawoo I think it gained enough of a reputation for it that there are a lot of english speaking creeps like that there.

Sorry, I understood what you meant. I was trying to say something a bit more subtle, which is to say, I think the reason why Pawoo has lost relevance over time is partly because of the fact that it got defederated a lot early on, and this has probably caused a bit of a downward spiral, broken window theory style. It discourages some legitimate usage of the platform, which inherently increases the ratio of unwanted usage to legitimate usage, which discourages legitimate usage further.

There are other things, too. Pawoo is still somewhat integrated with Pixiv, but I believe they sold it to Russel in 2018 or so (can't recall) off the news of new Japanese regulation regarding social media that they did not want to be involved in. This seemed to be a huge blow as well.

Then there's the fact that for Japanese sites, moderating English-language comments is very hard. The rules and moderation standards would ideally be kept consistent between languages, but this requires somehow both good communication with moderators and also moderators that speak fluent English. I doubt there is much proactive moderation of English content on Pixiv/Pawoo/Misskey/etc., and the majority of it is probably mostly ignored by Japanese users of the platform anyway. It's not like Twitter isn't full of a lot of the same stuff, especially since Twitter suspensions are treated as a joke or at worst annoyance by the majority of the userbase. (And honestly, it is also unclear to me that Japanese users would overwhelmingly be in favor of moderating text comments that express illicit interests anyway, so as long as the text itself isn't somehow illicit. This could be a blatant mischaracterization but they seem to err on the side of less restrictions to speech in general when it's in the gray area.)