Ranked

I have only been playing League now for about a year. Saying this I understand that I am not the best player and have no hopes of making challenger anytime soon. That being said, I feel that the lp system needs a change. If I am having a good game and my team feeds so hard that I cannot carry, how is it fair that I get punished and loose lp when we loose the game? If you are a solo que wouldn't it be better to have the lp system based on how you did in game? If I go 10/2/8 and we loose the game why do I get punished? I would say that was a good game for me. Or as a support I go 2/0/20 and get an S rank! Why should I loose lp?