What's The Point Of Being Positive In Game

I just played a game and really wanted to Ivern jg, Lee Sin locked in and acted all innocent so I went Ashe even though I don't adc very often. I get a good thresh who keeps ks'ing me and build a black cleaver, i was fine with the ks's by thresh but he goes 8/1 and the team starts yelling at me for doing no damage and being so far behind, I was never toxic or flamed, I went a role i don't play so our team didn't suffer but still got flamed for being positive in the end, sometimes the people in this game let me down