I think HN has aspects of social media, but I wouldn't call it that. I do get some similar feelings and "rewards" from reading and commenting on HN that I used to get with Facebook, Instagram, etc. But I quit FB & Insta years ago because those sites were overall making me feel bad and unhappy. HN isn't perfect, and I do occasionally get those negative feelings, but overall I enjoy reading the articles people post, and reading and discussing people's reactions to them.

Certainly I waste some amount of time on HN when I could or should be doing something else, but I think I've also learned a lot from HN, and get to read reasonable points of view that differ from my own.

I think HN's user moderation system (as well as HN's guidelines, and how the in-house moderators moderate and engage with the community) also push more toward HN being a discussion forum and not social media. While HN's moderation isn't perfect, it's not the engagement-at-all-costs popularity contest that plagues most social media sites and makes things unbearable.