Suggestion:
One should have the ability to leave feedback as soon as one is eliminated from a game.
At the moment, one cannot leave feedback until the game is finished. This can be anywhere from a few minutes to a few days after having been eliminated from a game. By the time the game ends and the person has a chance to add feedback, they may have forgotten about the game or their feedback.
When a person is eliminated from a game, the game is over for them. Therefor, it only makes sense that they should be able to leave their feedback then, rather than after everyone else has finished.