I agree with what you are saying but I think performance reviews can be extremely valuable. The issue is that at all big companies they are used for promotions, raises and bonuses. They aren't designed to accurately measure or predict these things.
To me, the right kind of review (and done every six months) is something that takes an employee only an hour and the same for the manager. Its only purpose is to set and review goals specific to the function and success of the team(s) the employee is/was on. The scores are more like pass/fail or exceeds/meets/doesn't meet expectations. It gives a regular structured time for employee growth review and can help with correcting communication and other soft skills.
That's a fair question. I think reviews shouldn't be about performance but rather about employee growth. It is a touch base to make sure everyone is on the same page. It should also direct an employee in their career path. These are discussions that also lead to "Would you like to manage people or remain an individual contributor?" "Okay, to do that you need to improve your skills at X".
As far as bonuses, I think they should just be split regardless of performance. I think raises are tied to promotion but if it is CoL, then people just get it.
As far as promotions go, this should be a broader discussion with lot of ancillary group managers as well and should focus on "Has this individual contributed at a level above their current pay and role?" "Do we all think this individual can handle this new role/level and be effective?" "Do we need more people at this role/level?"
To me, the right kind of review (and done every six months) is something that takes an employee only an hour and the same for the manager. Its only purpose is to set and review goals specific to the function and success of the team(s) the employee is/was on. The scores are more like pass/fail or exceeds/meets/doesn't meet expectations. It gives a regular structured time for employee growth review and can help with correcting communication and other soft skills.