This wouldn't always be true. You can't get better, if you don't have a chance at all. Using a 1-10 scale. If you are a 1, you will not get better playing against a 10. If you played against a 2, then yes, you would learn to get better. If you were allowed to work your way up the scale, you eventually become a 10. When I queue alone, I play against players at or around my skill level. This helps me learn the maps as I am not getting spawn killed constantly. I am able to hone my aim, and my movement as the players are only as good as I am.