The subjective valuation lead to quite a lot of nepotism and unfairness. There is techno-babble you can use to pick pretty much anyone if you are good enough with words.
I agree that's a problem of traditional management. The way to counter it is good management methods, in particular ensuring that reviews and promotions are cross-validated using other personnel, both horizontally and vertically. I'm sure you're right though, some bias will slip through.
The question you have to ask yourself is whether you are prepared to tolerate occasional suboptimal decisions for a metrics based evaluation that _corrupts the entire system_.
