Suggestion: Prevent the playing champs in Ranked unless they are Mastery 3 or higher.
Exactly what it says on the tin. Make it impossible to select champions in Ranked unless that player has a mastery of 3 or higher. Normal and Blind pick are unaffected. Those would be the queues that you are intended to learn said champions.
It's a simple win-win solution. Stops people from feeding on new champs they don't understand yet, as well as eliminating those that choose champs to play in ranked, saying "first time ______".