Yeah, you're right that even having users rate content is still limited.
I'd argue it almost definitely has to be better than engagement, though. It also has the potential to be less punitive to people who actually are thoughtful with what they like by using the likes as more of a classification problem and less shoving the same trash in everyone's face.
It's a hard problem, but sites aren't even attempting to actually attempt to do anything but tie you to a shitty dopamine loop.