The fundamental problem with recommendation engines are the platforms are forcing content on the users based on what increases engagement (and possibly ad $) on their platform -- not what is valuable to the user.
If I'm following a particular blogger, and their signal to noise ratio is 9:1, if they recommend an article it would be vrey likely I am also interested in it. If I'm following a larger group of people, I may be interested, in aggregate, what they are interested in. All very basic stuff that seems to have been abused and forgotten. Other than e-mail, rss is the odd man out in 2025 which also makes it so much more valuable.
Any third party RSS feed service could ingest these feeds and spit out whatever other type of recommended feed they want. The could just view a hn/reddit style feed solely with counts of the people they want to follow along with "vote" counts and some decay algorithm. They could have a chronological feed that just shows everything. The users are in control again, not Meta/Facebook/IG, Reddit, Bytedance, or etc.