I can agree that wins and losses shouldn't tell the whole story. It's not good to do terrible but you might bring things to the table that other players don't have that would give you guys the win (calling out, being a good teammate, map knowledge, etc.). The problem is that those things can't be measured by statistics, only by wins and losses.
On the other side you could be the best teammate in the world, call out, have the best KD, have the most map knowledge, stomp everybody's lights out, and still lose. Still happens to me a LOT.
I get what you're saying and I agree that wins and losses should still be a big part of the system.