I don't really get where this idea that criticism isn't allowed even comes from. All people do here is complain about literally everything! If you have something you want to convey to the devs then you should go ahead and do it. It may happen that people will disagree with you and you should expect that but you have to keep in mind that you aren't here to please the crowd. If you feel there is something that could be done better or that you want added to the game you should just go ahead and post it anyway.

I'm not sure if it was Yoshi-p or maybe Ion over at WoW that said that they appreciate feedback particularly when its specific and detailed. A lot of the times people will throw around buzzwords and ultimately say very little and I imagine that kind of feedback isn't all that helpful. I feel that's also something to keep in mind.