Tbh, that's why riot increased the IP price on new champs to 7300 or whatever it is now for the first week, to discourage people from purchasing them right off the bat and waiting to save a boatload of IP by getting them the following week. It is honestly effective, it's not nearly as bad as it used to be tbh. But to be fair, back when this was more problematic, champions were much easier to play.
I don't think they should ban them from ranked play, honestly they get their best feedback from ranked completion and ranked is the highest level of that outside of LCS. It's why you shouldn't really focus on winrates for the first week or two (unless they're incredibly high, then you know there's a problem) because it takes people forever to learn how to play them, play with them and against them. The truth is, at its highest level, that's how we learn about new champions and their capabilities so quickly. Sure, people will spam them in blind and normals galore but that's nota very accurate assessment because we know a lot of people don't take blind pick or even normal drafts seriously. So ranked data from the first two weeks alone is going to give you a much better perspective on a champions power level, difficulty to play and play with/against assessment than normals will, even though in all probability there's twice as many notmals played than ranked.
It's a double edged sword but it's a greater good for champion balancing, and after all we are in an ever changing game. Balance changes happen every patch, item changes on occasion and game mechanics even change. Do you want riot to disable all the ap items for a week after this? What about devourer? What about ADCs when the attack move command changed? This is an ever changing game that is patched every two weeks, you need to expect change and you can't exclude new champions from that because then you'd need to start making exceptions for other major changes, which is hilariously stupid to do and it would be hypocritical as hell to say you can't do that with other major changes but you can do it with champions.
In short, get over it. It's a part of the game and I'll give you a piece of advice: ban it. This stops your teammates from picking it if you're worried about them feeding with it. It can be frustrating because other bans might feel more important but it's pretty important to understand winning and losing too and if I think my teammate first timing a new champion in my ranked game increases my chances of losing, well, I dont chance it. I ban it and tell them to eat shit if they complain.
