My wife is an Industrial/Organizational psychologist. It's a thing I didn't even know existed until I met her. In her years of grad school education, she learned all about memory, learning, human interactions, workplace management, etc, everything relating to how human psychology affects work. Part of that was how to hire the right people.

It turns out there ARE things that can strongly indicate employee competence and success, but nearly no one uses them. People like her get hired, and then management promptly ignores their suggestions. On one of her job interviews, while waiting for a manager to come in for the interview, she got to talking shop with the HR rep who was co-conducting the interview. They talked a little bit socially afterwards too, and the HR rep agreed with my wife that the interview went terribly because it didn't focus on anything of real substance. The HR rep said to my wife, "we've been looking for someone like you for months, and we've seen a few as qualified as you, but not many, and we've never made an offer to folks like you because they won't listen to me, I keep getting overruled, and we're still without that position filled." They can't fill the job because they keep ignoring the advice they're paying for.

One example is the interview. It turns out the interview as we do it is actually one of the WORST ways to hire people, because it rewards all the wrong behaviors over the real needed skills. Simply scanning a resume isn't great either, you need to engage with the person on theoretical tasks, like an audition, rather than simply conversation and crazy questions.

TL;DR We know how t hire people, experts have it worked out, but we don't want to listen to their advice.