There's kbin, which is similar to lemmy, but not the same. They've picked up a decent number of users.

There's others too, but none that have really boomed the way lemmy and kbin have.

Fwiw, if you go to most of the more casual subs, particularly the meme/image based ones, probably won't notice the lost users from reddit because most of those were already swamped with reposts via bots and karma whores. But if you were into the useful side of reddit, there's a difference in quality and tone. A shit ton of the exodus was not only power users, but mods.

As much shit as mods get, they really are what keeps any forum from devolving into chaos and stupidity. It doesn't matter how "power mad" people think they are, what matters is that they put the time in to keep a given forum in a reliable state. The reliability is what left with the exodus.

Moderating a forum is a skill, not an inborn talent. It takes time to develop, and by the time the mods lost from there are replaced, and they get up to speed, it's months at least before they can start rebuilding the culture of a given forum. Even an experienced mod can take weeks to months to adapt to the culture of a given forum, assuming they don't make the mistake of trying to force a change.

Reddit straight up killed a lot of tools as well. The bot defense bot is essentially dead. That isn't something that can be replaced in the time the folks running it have given before they pull the plug all the way. Toolbox is alive, but lost the lead developer, and if it goes, moderating there becomes a major pain in the ass. I still keep an eye on a small handful of subs that aren't duplicated in some form elsewhere, via things like geddit and stealth, that are having major bot issues, and they aren't really mainstream. I can't imagine what the big subs are like in that regard now.

Reddit isn't going to "die", not soon. But, as often has been said when this comes up, the reddit we knew and loved is already dead. It's gone, and not coming back.