@alex
Step 1. Take everything from a big network that is naturally categorized and jam it into a linear feed.
Step 2. Build a super mega skynet AI that can sort the world in ascending order.
Hmmm... how about instead accept mortality and just don't do the step 1. Every "good" instance should have enough moderation to detect a spammer (or any other type of bot that is not properly announced) within itself. Users should be allowed to conveniently browse instances and follow them. No, you will not see everything that is "most important", such is life, deal with it.
I don't think the algorithms(tm) in the centralized networks were devised as a user convenience feature even if advertised as such. It's likely tools that arose naturally to cut costs and mitigate damages without having to hire and organize many 10s of thousands of people across the globe just as full-time moderators.