On Twitter and Instagram you follow users. That's user-first. You go there to see what so-and-so is saying, regardless of if it's about cats or politics or their dinner plans.

Reddit, lemmy, and traditional web forums are content first. You go to the video games subforum to talk about games, and the sports forum to talk about sports. You often don't even read the user names. You're there for the content.

User-first stuff tends to incentivize bad behavior, I think. It becomes more about who's saying it than what's said.

On Twitter and Instagram you follow users.

I don't know because I've never used them but can't you follow hash tags?