We’re not allowed to be blunt about a player’s performance in-game. Not without fluffing it up with purple prose and saturating it with fake niceties. Square wouldn’t dare entertain the thought of letting us give someone an actual factual F. Plus the idea is bound to be abused if implemented. Imagine trying your best and someone gives you an F because they don’t like your glam or your character’s race. It’s impossible to tell if the grade was honest or not.

Edit; I see you meant a computerized grading system. I doubt that would fly either. Casuals don’t want to know and don’t care.