"Replacing the CEO" isn't a panacea because most CEOs are pretty average, but when an exceptional CEO does take the helm, they can pull off some amazing feats (e.g. Satya Nadella).
I agree that most people are "average" (truism?), and that some are exceptional. And I agree that exceptional people sometimes achieve amazing feats in their field of endeavour. But what's so special about CEOs?
The scale of their impact when they are exceptional