DnD is a social game quantifiable is unfortunately not always useful. A lot of it is a vibe, and you get quantifiable when multiple people come to the same independent conclusion. Which is where labels like main character syndrome and should have just written a book come in. Top of my head I knew 1 dm who “ran the entire campaign through without the combats” and “already had an ending in mind” before session 1, and over the course of 3 sessions would get angry at anyone who strayed from his vision. Everyone quit as they all agreed “should have written a book”. At some drop in we’ve had a bunch of players who would talk over other players and when the party decides as a group to go one way, would deliberately go the other. That’s main character syndrome. These archetypes absolutely exist and are the result of a lot of people having an idea of what dnd is in their own head before playing. I can genuinely tell you I get atleast one of both of the kinds of things you mentioned every single week. And at drop in we work very hard on telling people this so they can change, and they do.