Why aren't american idol judges criticising contestants?

I couldn't agree more. Its what is missing on the show. Too much praise is starting to be like too much candy. I can't stand it and wait every week for someone to tell them they really didn't do well. I 'm sorry but Casey really sucked with his vocals with Who will Stop the Rain.. I was surprised at how dull it all came off. I thought he would be finished after that because it is supposedly a singing contest. I thought Simon was rude and bored and didn't really care but now I think they can find a medium somewhere and have at least one of them critique the singers. I have noticed that the other producers that help them practice for their tapings seem to be the critiquers now. Not so much the judges and that is kind of new this year.