People love bitching about ARURF because the tryhards can't play the same 20 champions ad nauseum to cheese out wins. That was literally all old URF was. If you weren't playing anything that was on an excessively small roster, you would lose, because everyone else would play the same shit like Riven, old Evelynn, old Urgot, Zed, and Maokai. It was fun for like the first day when you really didn't know what to expect in the mode, but it got old INCREDIBLY fast after seeing the same thing over and over and over and over again and not being able to have fun with things you wanted to pick if it wasn't meta because you would lose immediately if you picked it.
So URF was changed to ARURF to circumvent those tryhards who pretty much single handedly ruined the mode for everyone. Except the tryhards bitched and moaned about ARURF because they couldn't cheese wins anymore, and they continue to do it because they're unaware that their selfish actions in the game mode is what brought about ARURF in the first place.
But since ARURF has been going on for an entire month now, I think everyone is tired of it. As I said, the newness of it wears off fast, so that may also be a contributing factor.