@J12t It's a good question, and well worth asking ourselves. I feel like I addressed some of this last year on the podcast, when we looked at various social media as "meta-topical spaces", as part of the public sphere.
The community answer is a good one too.
But I think it's best answered by seeing how TikTok works, as it really aced the "media" part of social media, above all others.
Social Media is both the content and the community. It's watching a movie together and chatting about it.