Have you tried filtering the home page? I'm very new to Lemmy so my advice may not be the best, but on the home page (I'm' using lemmyusa), there is a "Location" option and I changed it from "All" to "Subscriptions". This way I only get the sub communities I've subscribed to.

I have not found a way to hide a sub community (i.e. hide "politics" or something) from the main feed.

If someone with more experience with Lemmy can sherd some additional advice for focusing content I would appreciate it!