The problem is, those existing systems were there for a reason. And I'd guess the reason usually was that the previous, less formal system also had their weaknesses. Most notably, they are very probably very subjective.

IMHO performance ratings and deciding who gets a promotion simply are very hard problems, and no good solutions. So people are always dissatisfied with the current approach, and so add rules and layer to fix it. Eventually, the system becomes unworkable and bloated, and are stripped down to the basics again. Which we currently observe.

But I wouldn't be surprised at all if the cycle continues, and more rules and formal processes will be added.