Proposal to reduce "toxicity" in ranked playlists; simple idea that is guaranteed to improve ranked

I have a simple change that I believe will reduce what players perceive as "toxic behavior" in ranked games. I don't think I need to spell out how the term toxic has evolved into a loosely thrown around response to anything not puppies and rainbows in chat.

My proposal is to make Mastery grades at the end of a match determine your LP gain/loss. Think about how many times you have done really well in a game, got an S grade, and then lost an absurd amount of LP. With my proposed change instead of losing say 20 LP you only lose 5 LP. In theory this immediately solves the problem of players giving up after the early game goes sour in a lane that is not their own. Everyone has had a game where a teammate feeds and you want to get out asap and into a new game but you have to wait until at least 20 minutes to even "attempt" a surrender. With this one simple change you incentivize players to keep playing for a high Mastery grade so they minimize their LP losses. This puts a huge emphasis on individual performance in solo/DQ. Right now the Mastery system is completely worthless as the only thing it shows is how often you play a particular champion, not how skilled you are at that champion. Riot pitched Mastery as a system designed to show off skill with a champion so why not make this change. Riot would need to give players a clear cut explanation of how the system works in terms of how it grades each role. This would lead to so many positive things for players, informing them of what they need to be doing in their roles in general, how to improve their play, what they are doing well, what they are not doing well, etc. The tutorial system is out of date and beyond 3rd party sources Riot does a terrible job of teaching players how to get better at their game.

TLDR: Tie Mastery grade at the end of matches into the amount of LP you gain/lose in ranked matches based on a metric set by Riot for each role in the game.

Please give an honest opinion of this proposal because I believe it would solve a lot of the problems faced by players who focus on primarily ranked playlists.