100% True.
Labor with no other skills, absolutely yes. Just needing to be a body to fill in to do the work will always be under valued because literally anyone can do it. However, even in those fields, there is a pretty huge range of pay between the people who truly are just bodies and the people who are skilled at those types of things and can do it faster, more accurately and with less micromanaging. As you get into the more skilled labor sectors, where the work can only be done by someone with an education, training or specific skill set, while still undervalued, the discrepancy is less pronounced.Want a super clear example? Slaves. They were paid, by virtue of being slaves, $0. And yet, entire economies were predicated on the value of their labor and what that labor produced.
Same goes for today. Labor is vastly devalued, and that's why wealth inequality is so grossly attenuated to the megarich. The idea that these wages are somehow the actual production value produced by that labor is just . . . factually wrong. Employees are almost always on the losing side of that evaluation. And that becomes more consistently true the lower on the totem pole we're talking; the exceptions are mostly at the executive level.
I agree with everything you're saying, I'll just add that the reason the exceptions are the executive level people is because it's those executives that make the call on how much everyone gets paid, including themselves, so of course they're going to be super well paid. The system is unfair, especially in cases where those executives can't do any of the work they're overseeing and the workers they're overseeing are the reason they're able to make so much (which is almost everywhere).
At some point in the iteration of a company the workers are absolutely essential workers, whereas the executives could probably disappear and not very much would change, at least in the short to medium term. Long term, companies need that high level oversight from talented individuals to navigate through the economy and stay relevant as things change. But that's a different discussion.