That just means HN's community and content is more relevant to you than other social media. Social media doesn't stop being social media if you find the content interesting nor does it stop being social media if it emphasizes one form of content over the other.
Social media was coined in the mid 2000s to separate new platforms built on social graphs and old platforms not. But it is common now to deny any difference.
Yes definitely. Again, audience and interests are different, but they are social media. Funny (sadly?) enough as a teenager I discovered IRC and was absolutely addicted and for a good 1.5 years spent every minute I could on IRC. I would use IRC at the school library between classes, at community college, at family friends' houses, in my own house, etc. We were poor at home but despite that I literally used any possible internet connected terminal to connect to IRC (and its resilience as a protocol made that really easy.) I had poor impulse control at that age but I do remember IRC a lot, and not in the most healthy way.
Also interestingly enough text-based social media (HN, Reddit, Bluesky, X) addict me way more than video based ones (like Tiktok, Youtube, or Instagram) do. I don't know if it's because it takes longer to digest the information through video than text but I do know that I have no problem with looking at pictures and videos and stopping for days/weeks, but once I get hooked on text it's really hard to stop. I even spent a year in middle school addicted to reading books though I had other things going on in my life at the time and books were a bit of an escape. I've had waves of HN addiction and definitely enjoy X and Bluesky because of the textual media of the experience.
As an adult I mostly grew out of these addictions but I can still feel their pull on me. Luckily I have enough going on in my offline life that digital life takes a backseat.
If you want to think of these in terms of "algorithms", then IRC and Usenet have a simple "chronological" algorithm to display posts while Reddit and HN use an "upvote" based engagement algorithm. X and more "modern" social networks may use more sophisticated algorithms but they're all just algorithms to return a sorted order of items.
