Qwiss At his peak he is definitely in that conversation, a few years ago was the driving force behind Milan winning the title. Right now nowhere near, like you say he lacks consistency and his stock has massively fallen. A few years ago every top club in the world would be fighting to sign him.
I do wonder if he just needs a change of environment, Milan isn't the Milan we all remember of the past. Being in a more competitive environment might get him going again but then his price and salary would need to reflect that.