You must be thinking of another sub. https://old.reddit.com/r/worldpolitics/ turned into a meme sub due to lack of moderation. People complained about it for years then finally gave up and left.

It's very easy for subs like that to become biased echo-chambers with the wrong mod

I agree, which is why moderation is an important topic that needs to be fixed for any reddit alternative to succeed https://old.reddit.com/r/RedditAlternatives/comments/ay0bc3/what_is_one_feature_you_expect_every_reddit/ehy9aka/. So far I think saidit has a way to go before solving all the problems with reddit.

For example, the problem of "random people who got there first" controlling subs isn't a solved problem here.

Tildes is doing some nice things, but the lack of ability to create a community like /r/fecaltransplant or /r/FMTClinics for example, means they're not a valid replacement in my case.