I think one of the major issues is that while the stick does function, it an overwhelming amount of cases the puck doesn't get "knocked away" any meaningful distance and the attacking player is simply able to pick the puck back up in one motion and continue with speed.
Also, and I will look to get some clips of this but attempt to pay attention while in game to the amount of time a d-man's stick is essentially in the air and not touching the ice, seems to be related to certain backward skating animations and the "stick check" animation comes out with the blade off the ice, this usually ends up with the stick getting caught up in the attacking player geometry.