This comes up often, particularly on Reddit, and I don't think we're doing us any favors by counting it as social media. It has a few substantial differences to Facebook, Instagram, TikTok, Twitter, et al:

- The focus isn't on connecting. It has a "friends" feature (I believe?), but the social graph is extremely weak.

- You are not expected to use your real name. On the contrary, it comes off as weird unless you're a celebrity.

- There is no algorithm maximizing engagement, or at least not a hyper personalized algorithm that analyzes your scrolling speed and every sensor under the sun feeding into a machine learning system designed by professional psychologists to keep you hooked.

- Individuality isn't as encouraged. The user name is small, and there are no avatars, or at least used to be (I don't use the new interface very much). The focus is on the content instead.

I suppose you can find a definition of "social media" that includes Reddit, and surely the differences are fluid, especially since we can recognize some efforts by Reddit to become more like the real social media sites, but I vote for putting it in a different category for the sake of discussion.

Reddit absolutely has algorithmic feeds since it ipo'ed (maybe earlier but I used third party apps so I wasn't subjected to them). 90% of my home page is bullshit I didn't ask for.

Yeah there is argument that reddit wasn't social media, but currently is trying to be

IMO, the old reddit UI wasn't, but the new one is, since they started the algo home page and showing stuff outside of your subreddits.