Ranked games do not show the prowess of a single person, but the prowess of your useless teammates.
I believe that one of the biggest problems with league is how you are awarded LP in ranked. For example, you may go 9999/0/9999 with 5000 cs at 20 minutes, but if your TEAM loses, then you will lose LP. I believe that if LP was awarded in a more individualized way, then there would be less complaints of "useless teammates"(which there are a lot of). If players lost less LP if they did good, but still lost the game, or they gained less LP if they won but did terribly, then there would be a better separation of the good from the bad. One good was to see this happen would be based on the ranking that you get at the end of a game. If you got an S+ but lost, maybe you should only lose 6 LP. But, if you get a D- but win, maybe you should only gain 6 LP. I would love to see this implemented into the game, and believe that this would be beneficial to the game altogether.