There are a couple of reasons why new champions should now be allowed on ranked for the first 2 weeks and those might be:
1. There are a lot of players learning them on PBE, and by the time it comes out, having knowledge over something others don't, will make the games quite unfunny.
First time abusers
2. There are A LOT of players picking it for the first time, having absolutely 0 knowledge about it's kit, therefore ruining the game for other 4 players.
3. Lack of LIVE servers balance
4. A waste of a ban! New releases are always getting focused on with bans in draft mode (normal or ranked), it creates shitloads of negativity from people that don't want to have it in the team, and even more negativity from people that want to play it and they're not allowed.
So, after 9 seasons! Can you please give them new champs a friendly 2 weeks of NO RANKED so people can get used to them and possibly collect data for balancing?
It's ok if you don't feel the same about this as i do tho.