> Reddit and Facebook are on the decline because both are full of slop. The problem is undermoderation, not overmoderation.

I don't think that's really the problem. I think it's just because Reddit and Facebook are too large to work, period - sort of what Kirkpatrick Sale was trying to get at in his book "Human Scale". Global systems of humans connected and interacting are probably doomed to this regardless of what mechanisms are instituted, unless those mechanisms limit in some way the local size of the interaction.