IMO Humans are better at understanding abstract things, taking into account not only technical requirements but also non-technical requirements. It would be horrible if I would need to argue with an AI about priorities, security concerns, etc.

Too many edge cases. Managers are working with people and we are complicated.

Will the AI Manager fight correctly about my promotion or my bonus? Will it make sure I have a good work-life balance? Will it considered I did an extraordinary job vs an underperforming job?