@shoofle "Social" media flipped the approach: instead of following a topic, the social media approach forced you to follow people. During that transition, multi-accounts became unpopular and in case of Facebook against their TOS.
With that, you got to learn the people and their option on all kinds of topics.
Discussing a specific topic became much harder, since the relationships were formed by general overlap.
@shoofle The dilemma became: should I follow someone, who shares a specific topic with me, but 90% of the time posts about topics I'm not interested in?
I think federation is key to go back to more topic-oriented communities. It restores the idea of multiple accounts, perhaps a general public profile, and several topic-oriented sub-accounts. Those could be completely isolated, or could be interlinked and occasionally share posts across.