I'm all for free speech and privacy. But in the 30+ years I've been online, the actual trendline I've observed is that anonymous, uncensored forums evolve quickly into a vector for delivering speech that promotes hate, violence, anti-consumer agendas and anti-democratic politics. And if I had an alternative to propose, I would do it, but I don't. I'm not (at all!) saying all internet discourse should be in censored forums. I'm just saying that when people spread lies and make threats with no accountability, the people most likely to defend that behavior are the ones who don't, themselves, feel threatened and/or might even believe the lie. And that's before we get into how these things become platforms for bots.
Unfortunately it is a necessary compromise, because free speech is essential to a working civilization.
It'd be interesting to see how that works in various languages, because there may be some selection bias. Most English-speaking countries have decent protections for all but the most abhorrent speech, and people who don't find their speech constrained may not bother with anonymous platforms. In non-democratic countries with more restrictions on political speech, maybe we'd find anonymous platforms full of pro-democracy dissidents.
Maybe something that would help these platforms is some kind of distributed or federated moderation, so you can avoid the icky stuff yourself even if it's still out there.