This idea is pretty popular. But I think in practice its become a way to maintain the power structure that in reality should be off-balanced.
Most "coaches" are not good at the game. And I agree that you probably don't need to be good at the game to coach if you're a people manager. But this idea of "coachable" seems to force players into a mindset that is authoritarian. You run in scrims and they critique your play? Based on what?
I know there are going to be a lot of people that disagree with me but think about this hypothetical. Imagine a coach who is very charismatic joins a team but they have zero knowledge outside of a couple of Youtube Videos about how you are supposed to play. This person brings the concept of "coachable" with them. If this person has a bad idea, objectively bad, how do you critique their idea? And what if the critique you provide threatens them? You point something out that is so outrageous that its very clear it's a lack of understanding...
I think the player just has to eat it. Waste their time and collect the paycheck.