Usenet was sorted by topic. Same people stick to the required topic in different forums.In the fediverse, you follow people, and therefore can't control very well what people post about. I follow some people because I am interested in technical topics, but I end muting some of those because some are very political, and I am not interested in some of these topics.

I don't think the Usenet model can be replicated on top of Fediverse. Not everyone sees instances as a topic thing (I host my own instance).