There should be a separate Statistics and Divisions/Leagues for Individual performance

Perhaps you can take the current K/D/A stats, and add a KDAP (Kill Death Assist Performance) stat, which adds your Kills + Assists and then subtracts that from your Deaths.

For example - if your score is 2/5/9. 2 kills + 9 assists = 11. Then 11 - 5 deaths = +6. So your KDAP would be +6, which is good. This would stop everyone from ignoring assists when people say things like "lol ur 2-5" and ignoring the 9 times you helped your team kill someone but didn't get the last hit.

Next, you can calculate if you won your lane. If you are Top lane, then the game knows who's tower was destroyed first. Add this to the Performance rating.

Then Riot can check your CS score according to the Match Length. What was your CS score at 10 minutes, 20 minutes, etc.

Did you assist in any Dragons or Barons? Add that to the score.

Doing things like this, would then enable Riot to accurately calculate your INDIVIDUAL performance in league of legends. Then a lot of us can stop caring about the Team Win/Lose aspect as it's a team game thing.