There's no need to post a hateful comment like that. If you don't like it, fine, then don't use it. It's OK to say why you don't like it, but don't call it garbage.
I don't want random posts to appear in my feed from communities I haven't subscribed to, but I want to have a feature that shows me suggestions for communities when I ask for it. That's a big difference. Right now it's (too) hard to find these communities.
Yes, that's what I mean by not trivial, a centralized system can do analysis like this a lot easier. But even on your own instance, they could find the N users with the most overlapping subscriptions and check which communities they follow to give you recommendations.
Crazy, I'm also in Europe and my provider stopped supporting MMS like a year ago