People try to improve upon a system so much, but the simplicity of the system is what makes it work. The more complex something is, the more room for errors or imbalance. Gaining Elo from your performance seems good when you think about, but there are numerous things that could happen that make a player get something they do not deserve, good or bad. For Example, a system revolving around getting Elo for kills, CS, and less deaths makes everyone play selfishly. Why the heck would I sacrifice myself for you so you can get a double? I get more Elo if I let you die and take the kills myself. The system works now because it doesn't matter your personal performance in game, but your teams. The system is meant for 1v1 chess, so symbolically your team should be 1, united. If you lose, you lose together, if you win, you win together. The game is a 1v1 match, if you will. (non-symbollically, basically your team is 1 entity, because 1v1 chess has 2 sides, the Elo system is only 2 sided.)