When I tried Mastodon, I found I couldn’t get the content I’m interested in there. I’m not really interested in following specific people; instead I want to see posts that fit my interests, regardless of who made them. Hence (apparently very unpopular on the Fediverse), I actually want an algorithm that can create a personalized content feed for me. Is there a platform that has that?
that sounds more like you want a platform like this one, why do you want Mastodon to do that when you have Lemmy/kbin etc to access these kinds of posts?
however, you can make Lists on masto where you can add certain hashtags and it will give you a feed of posts with those tags, have you tried that?