Personalized content discovery is not only about filter bubble and I believe the key word here is discovery, not shoving to your face in homepage. It can also mean discovering small subreddits that you might like. Or some old super popular posts that you might have missed.

Some of this would be forming a bubble (e.g. similarly minded subreddits to the ones you're following), and some not (e.g. somewhat random thing that you might like to binge read). You might find small subreddits on your own, that's great, but that might help other users.

No need to paint algorithmic stuff only in such dim light.