> it feels like this is much more a UX/social problem

It's not merely "like" that. That's what it is.

"Wiki" comes from the Hawaiian work for "quick". You spot an error, you click the button to change it, and the change is made. That's wiki.

"Open a pull request and get it approved" is not wiki. It's what the default collaboration model was before wikis and exactly why the wiki was invented (to replace it).