I think with any community, IRL or online, things start off great when they are small and the dynamics change unpredictably with they reach scale. "Subs" should help with this to a certain extent if people are able to branch off into smaller close-knit communities.

We see this often on reddit where some of the biggest subs evolve/devolve depending on the size and the nature of the content being posted and personalities of the moderators.

SN/reddit and other forums are more geared towards following topics / hobbies and communities whereas twitter/IG/tiktok is more about following personalities. So there is more of an incentive in the latter social media platforms to perform to grow an audience.