Literally Add 200 HP To Everyone
Being one-shot by so many things makes DPS carries less relevant because other champs also can just get a kill with no effort. It also makes skill expression more difficult because it's more about some lucky ambush etc. than outplaying in an extended fight.
I think this might be the thing most making it difficult to carry some games. People just get popped nearly instantly so it doesn't matter how good they are in some games. You can say that if they were better they wouldn't be in that position and that's true but it still makes it pretty binary. They almost can't react and live if they mess up just a little.