I would say anything with algorithmic personalized feed is a social media, and that's I would stop kids having access to.
I think the main danger is in the engagement maximisation done through these algorithmic feeds.
Mandate that the home/landing page of social media sites is a chronological display of people/artists/whatevers you've legitimately chosen to follow rather than maximization algorithm force feeding. For all users. The have to click to get to the algorithm zone. Problem solved.
I don't think that's really solved. Facebook had lots of engagement pre-feed. Reddit has lots of engagement even without personalisation. It's still going to be problematic for lots of people.
