I mentioned power poses and psychology because it occurred to me as an example since you happened to mention psychology. I don't personally have any knowledge regarding your attitudes towards psychology nor did I intend to frame what you said in any way.
Prior findings must be indeed critically evaluated. That's not the issue. The issue is refusing to even acknowledge them or to acknowledge current field wisdom due to some unwarranted sense of superiority. Taking the dangerous and daring approach to crossing expertise fields instead of being careful is fine, of course. Everyone is free to do whatever they want! But if the daring do fail, they will look like complete asses. They had been given plenty of warning before hand.
And, this is the key and the real reason why I'm saying all this, the daring will fail more often than the careful. The most frequent reason why people try to enter a new field is because they think they might have some superior insight on the matter, whereas the development of each field is chiefly constrained by the amount of data available to it. Ideas are never in short supply relative to data. This isn't to say that outsiders can't make meaningful contributions, or that cross-field collaboration is useless, far from it. But that there isn't much that can done beyond what's warranted by the data.
I'll pass up the opportunity to talk about Musk, because I don't feel I'm qualified to do it.
But as for your nitpick: I don't see why top performers incorrectly gauging their own ability would be "okay". They would pass up great opportunities because they perceive their ability to be lower than what it actually is, and they might experience unwarranted anxiety and feelings of inadequacy (something like an impostor syndrome) if they incorrectly perceive their ability to be lower that that of their peers. There are many ways in which this might not be "okay".