It’s a myth so widely pushed and accepted over the decades that just calling it a myth won’t be accepted as an argument against it at this point.

What I think is interesting is that this sense of fiduciary duty can be used by a company to do whatever they want. Mass layoffs are part of a fiduciary duty to cut costs. Mass hirings are part of a fiduciary duty to expand operations for growth. At this point it’s less a myth and more an excuse for doing whatever.