Why do people blame me?

Dear riot. Why do people blame me in every game? I just had a game that my adc reported me and being toxic. He told me to buy sightstone first after i said wtf? I tried to save ur life and u didnt run? And am i wrong if someone is being salty to talk back and not mute? Well im sorry because ive played a server where reports are useless and people are toxic and muting isnt a thing. And he blame me for leaving him and die and said wish he had support. But im not only his support, im support for the team and his blaming me that im bad but my team is trolling. The shen called jg and shyvana took jg and i said i can go supp and shen or tryndamere can go mid and shen said im going mid and he switch his summoners to ignite and flash and when the game starts i saw him had flash and smite and with jg item. And when shyvana was jungling shen flash and smite it and they both fed. Pls response to me on what to do when there's ppl like that. Im being toxic because I dont want them to blame me but the fact is my other team is the one whose not doing well. im tired of getting reports and getting the 5 games que and need to wait 20mins