I think "recommendations" are polarising rather than exclusively a (business) mistake. some people, like me, you and probably most of HN, see them as an intrusive waste of time and go out of their way to avoid them; however, I would imagine there is a very large slice of society that doesn't actively moderate how they spend their free time, or really question the things they're presented with online, to whom "recommendations" will have become a very engaging way to find new content and spend their time. that description isn't a euphemism for "stupid" either. I know plenty of intelligent people who scroll through a feed endlessly when they want a way to occupy their mind
Recommendation feed engines probably gives encouraging numbers in the beginning, until the users realize that they are fed BS clickbait instead of baby pictures and other gossip.
While I am quite sure some are hooked on the feed, the core of Facebook (friend gossip) is gone.