Ranked is not the time to find out if the new champ is "good" against another
I'm speaking through the experience of my last played game.
The enemy mid laner chose Kat as first pick. Perfect chance to, I don't know, COUNTER HER?
Our mid laner took Zoe, on the excuse of wanting to take her against Kat and see if she's good.
Apparently not, because she fed the hell out of Kat which she snowballed out of control and we lost the game.
In Ranked, that is not the time to be doing shit like that. Do it in normals or bot, where you can PRACTICE it. Because ranked, you need to be on top of your game and not just picking a champ to see if they are good against another.
Don't ruin other peoples games and make them lose LP because of that!