My experience so far has been:

• "default" reddit, like /r/popular etc. has been worse, because reddit started using some form of "the algorithm" which pretty aggressively pushes controversial subreddits with high engagement, and those tend to be dumb and toxic. Amitheasshole, twohottakes etc. are the most obvious ones.

• customized, highly selective reddit with as much crap from the frontpage as possible unsubscribed from is not significantly worse than a year ago, but then again, it was already pretty bad a year ago. Since the API changes I've had 3 people block me to get the last word in an argument, for simply disagreeing with them, without me being an asshole. This is quite annoying in a small subreddit where such a person posts regularly, but it may have just been bad luck.

• Lemmy... Well, 3 things that I probably dislike about reddit the most, not because they're the worst things that happen there, but because they're so damn prevalent, are overmoderation (heavy handed deletions of posts and comment trees, unnecessarily locking threads that are even mildly controversial, things like banning people for ever posting in a controversial community etc.), strong american partisanship where if people realize you don't agree with them on everything with regards to society/politics/culture wars, they immediately assume you're from the opposite american camp and that you must have bad intentions, and finally simply people not being very smart on average.

Well, all three of those problems seem to be just as prevalent on large Lemmy instances, the first two even more in some places. And whereas on reddit many people understood that you're probably not realistically going to be able to create an alternative subreddit to some huge default with hundreds of thousands of users, so the "go make your own subreddit" copout is not very practical, here "go make your own instance" seems to be one of the default reactions to any criticisms.

That said, Tildes seems to be doing okay. It's even smaller and it doesn't really try to be a reddit alternative, but it's considerably smarter and more sane on average than both Reddit and Lemmy.