Ranked Suggestion | Champion Restrictions
I've seen this being a reocurring issue; People play champions they have little to no experience with in Ranked. Don't get me wrong, I understand that finding new champions is good and all, that's what we all do, but I don't think it belongs in Ranked.
My suggestion to solve this, at least partially, would be to restrict champions in Ranked to champions you have achieved S ranks a few times or reached Mastery Rank 5. This suggest that you know the champion well enough to perform to some degree at least.
Yes I know, you would have to go to Draft or Blind and actually play something that isn't ranked, but that's exactly the point of these game modes. If you are a highly skilled player then you will reach S-ranks in no time and get to jump straight into Ranked with that champion anyway, no need to level it up. And if you're the opposite, someone who struggles doing that, then that's exactly why you shouldn't bring it into ranked until you have the experience necessary to perform properly, without letting your team down by default.
Of course, people have bad days sometimes. It happens, and I'm fine with that. One team has to lose and everyone can't be at their peak performance every day at every hour, but playing a champion for the first time in Ranked is something I think is a fundemental flaw in the ranked system.