You CLEARLY misunderstood something at some point here. I'm not saying anything about having a KDA of 0.5, I'm saying if someone is dying on average 2 times per minute. Take into account things like greyscreen time and time running back to lane, and dying twice in one minute is actually something you have to work towards.
To have a competitive mode there has to be some threshold for punishably bad playing, or the whole system loses value. You should not be allowed to ruin others' games with lasting score changes just because you can't be bothered to try that game. If you are legitimately dying twice every minute on average (and not just stacking MS and running it down to the enemy tower) then you have either picked up a champion for the first time into their hardest counter played by a onetrick (in which case why are you first-timing in Ranked, especially without having at least glanced at a guide first), or you have no concept of how to play even remotely safe and are going to keep feeding the enemy for the entire game through sheer bloody-minded stubborn-ness and belief that you can make no mistake.
I'm not saying roll this out to Normals or Bots, because there has to be learning space somewhere, but to come into Ranked and manage to die that much, you deserve a ban for what you are doing to the poor bastards who are forced onto your team and their MMR+LP.