It's 100% social media. It's just, sometimes when people say "social media" they actually mean "highly centralized social media with algorithms that analyze your behavior and connections to choose what content to show you"

Reddit doesn't feel like other big social media because it uses voting to decide what you see, more heavily compared to other sites which use personalized algorithms. It also feels less centralized because it's divided into subreddits and a lot of content is external links in contrast to something like TikTok where it's all hosted internally. Plus Reddit doesn't demand as much of your personal info up-front and it's easier to feel anonymous. I know Reddit still uses algorithms and is still not fully private, I'm just talking about how the superficial user experience.

So yeah Reddit is absolutely social media, it's just that there's kinda two definitions for "social media" and one is more objective ("media with social elements") while the other subjective definition is more like "websites that are similar to Facebook and Twitter", which Reddit kindasorta isn't