Understand that most of the general population operates on the level of "Somebody said something on the Internet that offends me; how could this have happened?" And that the maximum amount of effort they're willing to put in to rectify this situation is clicking a button. The realistic amount is that they wish it never happened in the first place. That's the level of user-friendliness needed to run a mass-market consumer service.
That being said I don't think it's impossible to have such a system in a decentralized way, there are incentive structures you could build to handle this.
Moderation is a fundamental requirement of any social system, and it's one of the two things that Web3 can't yet address meaningfully -- the other being addressability.
I think the problem is that by and large, users are not willing to do this work themselves. When faced with a social platform that has a lot of jackasses on it, rather than individually curate their experience to remove the jackasses, most of them just leave the platform and find another one where this work is done for them already.
And this is why social networks have abuse teams. If it were totally up to them, they'd rather save themselves the expense, but users have shown that they will leave a platform that doesn't moderate, and so all social platforms are eventually forced to.