Pls change grade system in season 9

Instead of the so called complicated metric system they say they are using. The grade system should decided on a set amount of kills, deaths, cs, and assists based on the role the character is and the lane they are going, that is affected if you get more or less of the prior. In most one of my games I had went irelia top and was 14/0/5 and the game ended roughly around 18 minutes. Though apparently I was given an A- and my friend who was being master yi and also top with me got an A+ and went 5/4/12 with less than half the cs I had earned and less wards. Maybe I have the system wrong but there definitely needs to be a change on the grade system.