Honestly just sick of players playing newly released champions in ranked play and losing and feeding with them. It's happened so many times already with Aurelion Sol. Now I'm not saying it's impossible to be good with new champions in ranked because I have seen it before, but I just feel like it would be better overall to not allow new champs in ranked for like a week or two. Give people time to play whatever new champion in normal games THEN come to ranked.
edit: Not to mention it is often people in ranked will not know how to play against or with these new champions, unbalancing the gameplay of ranked.