From what I see, ActivityPub doesn’t seem to solve the problem of sorting or prioritizing content. In fact, I believe RSS wins here, because it is easier to do this on the client side with RSS, as it is assumed the client has all the content from the RSS feed without any biased order, whereas with activity pub, it varies by provider and instance.
Sorting and filtering can be done well on the client side, and the plus side is the user can have a ton of choice here. It just so happens that our algorithms for that in the open source world are no match for the addiction-inducing ones of Twitter and others.