I think the big problem in link aggregation is how to sort/prioritize content for the end user. RSS does not provide a way to do this, nor should it as far as I’m concerned. It should simply be about public content being tagged in a standardized way for any app to come along and organize it using whatever algorithm.
A simple RSS reader has the problem that the more prolific sites will tend to flood your feed and make it tedious to scroll through miles of links. Commercial news portals try to learn your tastes through some sort of machine learning algorithm and direct content accordingly. This sounds like a good idea in theory, but tends to build echo chambers around people that reinforce their biases, and that hasn’t done a lot of good for the world to put it mildly.
The lemmy approach is to use one of a number of sorting algorithms built atop a crowd-sourced voting model. It may not be perfect, but I prefer it to being psychoanalyzed by an AI.
Btw there was a post from about a month ago where someone was offering to make any RSS feed into a community. I’ve subscribed to a few of them and it’s actually pretty awesome.