I don't disagree! But the way I've mostly seen capable people fail is by becoming afraid to push themselves beyond the limits of their innate capabilities, into the territory where people stop telling them how smart they are and every step forward is paid for with pain, Little-Mermaid style.

By contrast, people who have not learned to put so much value on their being "above average" don't have as much trouble pushing further into that painful territory because to them, everything is pain anyway.

That way I've seen people with little talent go further than, or at least catch up to others who have it in abdundance, through discipline and work. My formative experience in that respect is from a different life when I was studying for a modern drums degree.