Please Disband Grading System

Correct me if I'm wrong, but I believe the grading system is based almost entirely on your KDA?

I can be a Tristana killing the same lane opponent who has no skill at this game all the time. If I took 0 towers, didn't do anything for my team, chased into jungle and died a few times, and did other things, why do I deserve an S?

I can be Zac taking good positions in team-fights but ultimately dying while setting my team up for inhib, good ganks, securing objectives. If I went 2/7/16 do I really deserve that B while the Tristana deserves an S?

Point is, congrats, you manage to kill someone! That doesn't mean you have in any way a high skill level.

I don't get the grading system at all, I think it just needs to be removed.