> Someone should make a social media site with inverted dynamics- users who only spend a few minutes per day on the site and post once every few weeks should be treated as the influential power users, while the people lurking and scrolling for 10 hours per day are deprioritized.

The problem is most users are the "casuals", by a wide margin, in general; and a lot of them are also "weirdos" in different ways. Some of them will be obsessed with a different site; others have serious issues in spite of all the forms of social proof you describe.