Fantastic replies so far, ladies and gents. It's certainly one of those topics that doesn't have a right or wrong answer, but [@pugbutter] had a really excellent point and it being a thing that comes from the right place but can be seen as backseat GMing/ an unintentional "I'm better than you, let me fix you" mentality. I rather agree with that sentiment, and I think it's why most people err on the side of politeness.

Let's say a GM had a form, so to speak, where players can optionally sign off their willingness to receive critism and advice or something of that nature where it's established and everyone on board with it declared their openness to the concept? Would that be something that would have merit in a roleplay?