Facebook in the mid 2000s was pretty good. It was a chronological timeline of your friends’ posts along with a photo album. It was like LiveJournal but with a much better UI.

IMHO, having effective parental controls would be good enough.

no algorithmic content driving the variable reward schedule in order to induce compulsive behavior, just content I've explicitly selected and a willingness to say "we've run out of content" instead of just filling the infinite feed with whatever

Anything without a feed backed by a recommender system.

Front Porch Forum is one example of a relatively good social network. It's made possible by the founders not aiming to become billionaires. This is another necessary property of basically anything good.