From my perspective as a user that has been on reddit for a while, its been on a downhill slide for a long time now. The moderation mechanisms there are really becoming the downfall. Its like police or politicians, the position attracts the very qualities that would make you unsuitable for such authority.

This really is a bigger and more complicated problem than I think most people realize. I helped moderate some larger subreddits for a while, but I burned out hard and will definitely never be doing it again.

You've got the people who really did care, at some point, but all of their empathy for the people they're supposed to be serving got ground down by the insults and derision that moderators always have to put up with, until issuing bans and removing posts and comments becomes rote and they don't see the humanity or the nuance anymore.

You've got people who seemed reasonable when they applied to become a moderator, but as more trust and autonomy is afforded to them they change and become outright abusive. Presumably because it's the only thing in their life that makes them feel powerful. And if they've been around for long enough and moderated actively enough, then removing them can be a whole stressful ordeal that blows a big hole in a team's ability to keep up with the mod queue.

And you've got people who do care, and who are able to take abuse from the community without it affecting their approach to moderation. But for these people, all the drama that arises in trying to work on a team with the former two kinds of moderators becomes increasingly demotivating, until they burn out and step away.

And god forbid you try to help moderate a subreddit that actually matters. On top of everything else, you will have bad actors actively trying to infiltrate the moderation team, to bring in new moderators with a certain agenda and to push out old ones. Or you'll have those who are determined to find a way to personally profit from having a position of power in a large online community, even at the cost of the community itself. I still don't know how one keeps these people out, once they've taken an interest.

I think there are some things that can help. I've seen that, on reddit, having a top moderator who is disengaged from normal moderation but who will keep tabs and step in like a benevolent dictator to arbitrate internal disputes and ensure that there are decisive resolutions can keep larger moderation teams more stable for longer. This way the top moderator isn't so involved and won't burn out, and everyone below them on the moderator list knows that there is someone they are accountable to. (Of course, this all hinges on the top moderator being suited to this kind of role.)

But even so, once a community grows past a certain point, I think it's just not viable to run it off the backs of volunteers anymore.