By human nature, any kind of mod system lacks the quality people dream of but it will never happen. Nobody can be truly objective or unbiased, so we wind up with the same thing whether it's Lemmy or Reddit or any other platform. It's the same problem no matter what.

Also, what does good or useful speech count as? Like what are we even trying to defend with that?

I will argue that the whole centralized aspect is what actually made Reddit so mainstream. Everybody has probably used it at some point by now. It just had whatever you could think of and while that seems alright, the problem with Reddit is still the corporate and tech bros controlling what gets to run on the platform. Doesn't mean instances or comms won't also get fed similar or their own propaganda but go figure.