Perhaps we should task the curators with increasing their diligence while curating?
Curating is a job. It's often thankless work, and the reward isn't great. Until someone can feed a family and live off curation rewards, I very much doubt we'll have a chance at the professionalism you seek.
I agree with what you say about rewards migrating to the 2nd layer, but I can't see that as a realistic occurrence before rc's have value.
I'm not sure how one begets the other. But assuming it does, if RC's become much more valuable, that means we've grown massively. But if we've grown massively, then content moderation is even more complex. Decentralizing to L2 allows for competing approaches of tackling the problems that arise.