The rating system is giving CS too much weight

I've had games where I dealt most damage, almost never died, had best KDA, led my team to win, and only end up getting A+ because I decided to give my teammates CS after I'm full build, since I got a lot of golds from Kills. Which means I probably have something like 200+ cs in a 40+ game, and that seems terrible to this rating system. BUT BITCH I WAS FULL BUILD Like what do you expect me to do? I've seen GP players who have this farming condition and can't stop taking every single creep from teammates after having full build already while mumbling "muh i was help pushing i wasn't farming you fuking retard" AND I DON'T WANT TO BE ASSHOLES LIKE THAT, I FEEL DISGUSTED WHEN I NOTICED YOUR SYSTEM IS ENCOURAGING THIS KIND OF BEHAVIOR Meanwhile I've also seen ADC who dealt least damage among her team except for support, having KDA like 6/5/10, still end up getting S- because she was Sivir and she had way more CS than anyone else, although she didn't put those gold to any good use.