Comment by charles_f
This should have a (2021) tag.
Whatever system you create to make them semi-objective, managers will cut corners and just default back to taking the ranking they need to produce, put people in, then post-rationalize. I have been in enough of these in large companies with complicated frameworks to derive the conclusion that these frameworks are just a facade of fairness.
Even the simplest scale saying "at this level you should XXX" where you're supposed to align examples is ignored. Let alone more complex things where you're supposed to compare impact with opportunity to kinda balance for people who work on less shiny projects.
Sure, the odd manager will care, but the vast majority will just default back to a basic "did do big project I feel like important? Yes, then good boy/gal. Nah, then you should raise yar impact".
Compose that with the fact that these are supposedly chaperoned by the top, which is traditionally filled with people who have been there since you were an infant and definitely don't want to change how they do things, and you create morose cultures where this will never change.
On top of that, it's arguably very hard to follow the work and performance of 6-10 people, especially now that we're remote, and especially when every middle level manager is dawned in meetings rather than managing. If you mix this with a low level (or absence) of training, then it's impossible to produce something remotely fair.
And finally, it's almost an impossible task to do. Rankings and evaluations by a single person are an extremely noisy process. Sure, sometimes there's someone with an obvious problem who doesn't do what they should, or a star who's carrying projects on their sole back (and yet again, are they really, or is that how it's seen). Most of the time, the distinction between abvo and below average is too fine to be reliably judged by a couple managers