What about ganks? Can't mid and the jungler gank early game and shut them down to reset the lane? Why not do a lane swap midgame? Tell the person feeding to play passively, or give them a tip on how to win trades/avoid taking damage? I mean, maybe they forgot you can interrupt channeled abilities, or you can buy an item to counter certain spells.
the game is done unless they play like retarded chimpanzees. Which they may at your level of play, but they don't at Diamond.
I don't appreciate the backhanded insult, but if you're Diamond then you should know how to come back in a game. Even at my elo, where we're all "retarded chimpanzees," I'm still capable of strategic thought and shutting down a fed Riven by using a combination of wards and communication.
You're angry, I get it. But there's always something that can be done in a game, especially to prevent a problem BEFORE it happens. If someone is feeding, maybe another lane can swap with them so they can farm. A well-farmed carry is just as good as a fed one. If someone is feeding, maybe your team should have prevented the feeding after (or even before) the very first death.
And if someone is actually that bad as your mood indicates, then they should be dropping LP consistently and you won't see them anymore if you play at a consistently better level of gameplay.