How riot can easily impliment a change to improve the experience players have in ranked play
The system already exists oddly enough. The real problem with ranked play is that everyone on both the winning team and losing team are either rewarded or punished equally which creates a big meaningless pile of chaos of players with their skill of play rarely objectively measuring their skill at the game. I can go 0/20/0 and win a game where the rest of my team went 20/0/20 and I will walk away from that ranked match with the EXACT SAME REWARD as my teammates who clearly are superior players who deserve a far larger reward than I do for that win, this isn't fair and it only ensures a longer number of games will be required to sift players to their true rank. The current system also leads to immense passive toxicity, you all seen it, player x is angry and sabotage's the match in a way that isn't intentional feeding, and they don't type mean things and thus they will never been punished. I am talking about that silent player who QQ's they didn't get a gank and then sits alone in the lane or jungle never participating in the game for example turning the game essentially into a 4 v 5.
Riot already implemented a system that gauges a players relative contribution based on performance metrics That grading you get a the end of the game... All riot has to do is implement a scaling LP reward or penalty that is augmented by that scale. So when that person goes 1/12/4 and gets a C is lucky enough to be on the winning team they get a very small reward of LP, and vice verse that person who goes 20/2/12 gets and S+ on the losing team with everyone else being 1/12/5 C rating they get a very mild penalty for that loss. Suddenly the system will start to sift people faster and more accurately to their proper rank and reduce the noise created by all the people who are carried or feed hard.
It will also help curb a lot of the passive toxicity which many of us find far more frustrating than a player who types omg jungle sux.
TLDR Use the current grading system to tailor lp gains and loses to the players contribution or lack thereof. Average performance would get typical lp gains or losses, below average will get lower lp gains or larger losses, and a higher performance would get greater gains or lesser losses all relative to their teams average performance.