The difficulty for getting an S on a champion that doesn't get alot of kills is ridiculous

I can go 1/0/6 in a 20 minute game as shen against a bot lane that is really hard to kill and i only get an A- as my score meanwhile my mid lane fizz just gets like 7 kills and magically gets an S- even though killing people with fizz is so easy.

The whole system needs to be toned down so champions like shen or other low kill champions have a chance to reach mastery 6