Humans contributing tags for filters would be like fighting the tide with a spoon.

Isn't that what you're literally advocating for here? I don't see the practical difference between having users reporting AI content versus users reporting AI content that isn't correctly labeled as such.

I stand behind what I said. Give people the option to filter it out of their own feeds if they want to. I don't wish to push my own content preferences onto people with different tastes. Curating your own feed is the way to go. Not top down control from the tech companies themselves.