He doesn't play a lick of defense. Imagine if the other stars around the league completely abandoned the 2nd half of the ice and cherry picked for 2 on 1's all game long what their production would look like. Now imagine they also had McDavid feeding them on the PP (in which they draw top of the league in PP opportunities). Then all he has to do is let the goalie and coach be the scapegoat.
He is obviously an incredible player. I enjoy watching him a lot, and especially love watching him on the PP and how he can score on the slimmest angles. But if you watch him it is obvious why the team has never won anything in the postseason..