That is the worst thing about him. It cant be the philosophy's fault, it must either be the players that are too slow or not good enough, or the injuries, or missed chances.
I think its also a hindrance to himself as a manager. The period between 2000 to 2004 was a disastrous one for him as manager , but he never tried to adapt or learn from it. I think for me, what made Sir Alex so special, is that in 2005, he reached a point where he realized that he had to evolve, or he would die out.
Van Gaal has gone on record saying that he believes that his philosophy is the right one, and he will never change it.
He seems to try to enforce his philosophy on his team, then after months of it not working, he'll stumble across something that works. When the danger has passed, he then seeks to revert to the same original philosophy that isnt working. That is exactly what he did this summer. Its baffling really.