Individual instances will have to moderate themselves. If they become chaotic, other instances should unfederate them. But as users, you should also subscribe to communities you think are behaving well and block users/communities that are not.

Also, I have seen some users who are "grabbing" as many communities as possible, namely @Hurts@lemmy.world. Dude is moderating 60 communities, in an instance that started a few days ago.. He is not building the communities, he is just power tripping it seems. @ruud@ruud@lemmy.world, something might have to be done about that in the future. I suggest some sort of "requestcommunity", in which you can apply to become the mod of said community, if community is being badly run (or not run at all).