I don't see sites that just have user discussions as social media. To me they're essentially usenet but on a web site. I'd say to qualify as social media you

I don't see sites that just have user discussions as social media. To me they're essentially usenet but on a web site. I'd say to qualify as social media you need to make the experience about connecting people with each other or with groups, and finding people to connect with. Things like Instagram, TikTok, Facebook and Twitter are all definitely social media. A site that just posts news headlines that people comment on is not really social media IMHO.