You keep missing that the problem is engagement optimization, not political divisive/disinformation per se.

A site that optimizes for content that people heavily interact with (engagement) is different than a site that prioritizes the relationship type between users (friends original content > public figure OC > shares > etc) or positive response (upvotes), etc

None of these many other systems rely on discerning the specific nature of content or making sure it’s of some certain arbitrary moral character. But they each lead the network as a whole to favor different kinds of content and so the experience for users ends up different. And it’s already known that social media sites can be successful using these other techniques.