Employee performance reviews are always a subjective process. Owing to the magnitude of uncertainty in human behavior, the reviews cannot be completely automated. However certain decision points which could be quantified, can be automated. Certain inputs can be offered by AI, which helps in reviewing. AI can make a powerful DSS, but not handle the subjective reviews altogether.
The automated performance reviews would be in the wishlist of many managers, who find performance reviews a nuisance.
At the end of the day, I would like to hear that I did a good job, from a person and not from a machine.