What's shocking was there was a time at google where management was forced to prove their existence was necessary.
https://rework.withgoogle.com/subjects/managers/
One of the problems of course is giving managers feedback. It's hard. It's ugly sometimes. It's always fraught with risk, since you are the one without typically any power in the situation.
But the true canary in the coal mine is when the good employees feel like their feedback isn't heeded, and then they leave. And they can because well, they're good. And HR, having gone through all the trouble of hiring the best and the brightest, are just walking them out the door.
If HR stands up for the employees, then that's a different story than HR being lap dogs for the powerful. Currently turnover numbers probably just sits on page 248 in a footnote of the quarterly HR report and lands on some executive's desk who may or may not care about it.
As an aside, I once told an HR director that the problem with HR is the name: Human Resources -- as in "Humans are Resources". She told me the inside joke at her company was that HR stood for "Happiness Removal".