So yes i do think it is social media. But they are more akin to the old internet, or Facebook before it got massive and bad.
For exampke? There is not a massive algorithm, especially a personalized algorithm (obviously Top and Hot are technically algorithms, but they democratically place popular posts to anyone who hasn't blocked/is following the community).
For many comparisons they are obviously social media, but for other types of comparisons I don't think it's a great match.