Now I re-read the Growth mindset part: It made your article better, thanks! More critique.

There is a saying: If you are the smartest one in the room - you are in the wrong room!

However, your point on self-esteem is very valid. I believe the secret is in being gradual. Motivation can do wonders.

To add points, Dunning-Kruger effect seems to be not fair for the people well above mediocrity. So for those rare ones your advice may be harmful: They are already convinced they are not up to the task (unless they have other useful personality traits for the situation like formidable self-confidence). Coming to adequate environment in the field they chose (MIT, Oxford, Harvard, etc) can really unlock their potential.