Think about it. Riven, Vayne, hec, morgana, kayle, jax, irelia.
Common picks im seeing at around gold elo. If a certain team lacks any of these champions, due to the scaling, it's just a solid statement that you have less chance to win.
looking at it from champion statistics and over all play ratio POV, it appears to be a bit determined. Its also a chance of the 50/50 coin flip of who and what plays better or worse depending on the match making. Just feels like a cluster. Im at a loss of words to describe it, but I think the boards have done a decent job at it overall.
edited: right im aruging the point of champion pick is more reliant than player skill level.