It's 2018, can we please stop allowing players to learn new champions in ranked?

I'm really sick of losing games because someone is taking a champion into a Diamond ranked game for the first time and feeding their ass off.

i.e. my last game had a first time Vel'koz who died twice to Zed before level 6, then a couple more times after level 6, and finished his first item (Hourglass) around 20 minutes. He did not take Stopwatch. I ganked for him a few times, but whenever I ganked, he would just immediately ult without using any other abilities (essentially doing no damage).

He continued to repeat this (just ulting as soon as team fights start, without using his other abilities to apply passive stacks) for the entire game. It was clear that he had absolutely no idea how to play Vel'koz. When someone suggested not ulting until his passive procs, he got defensive and started raging.

This is not competitive behavior, yet it happens constantly.