Wouldn't that heavily punish a support main who isn't intentionally feeding but sacrificing themself a lot for horribly positioned carries? Also, if they are doing that bad in every game ever, they just might have horrible mechanics and aren't doing well in LoL.
You're really oversimplifying the problem and overstating how many other games punish intentional feeding. When I left WoW, intentional feeding wasn't punishable for arena games. When I was playing HotS, there was no option in the reporting for intentional feeding.
I get that you are upset. However, being toxic is not an understandable or acceptable response to toxicity. It is a self feeding cycle that robs any enjoyment from a game. The fact that you're being sort of rude in your responses to people with differing opinions to your opinions only leads everyone else to believe that your ban was justified as you are toxic to other people that point out flaws in your reasoning.