HN is social media only in strictly technical sense of the term.
HN isn't optimized daily for engagement like FB and IG are. There isn't a single image, or video on website. Ads (for YC companies) sometimes show up and are rare. Color scheme-wise it is very plain (and should stay like that). HN is not hidden behind login wall. It is not tracking you. You can access HN fully anonymously, and create throwaway accounts for posting.
HN isn't social media at all because it doesn't have a social graph (you can't follow people here).
there's no need to "optimize" it already has the basic loop. stochastic reward (interesting news, interesting comments/replies), gamification (points go up!), and no real social interaction. (no connection, some performative elements, ie. comments are written not just to one known person or a small group of people you know.)
the things you mention all exploit this loop for monetization. I agree it's great that HN is not, but that doesn't mean it won't tickle our brains.