I don't know how possible it was for Van Gaal to fix this mess but he needed to do a much better job with his lists. The overpaying I can't really criticize him for because Ed buys the players. There have been quite a few missed calls as a coach. The style of football. The use of Rooney, Herrera, Darmian, and Fellaini.
At this point I don't know what can be done. We need a new CB, but the first decision needs to be how do United wasnt to play football. You buy players that fit the formation, not the other way around, look at Di Maria last year and the attack this year in general. If we play a more attacking style, a 4-2-3-1 like Chelsea/Madrid, a new right forward/midfielder is needed. Mata doesn't prefer to play there and Rooney isn't the ideal player in any position any more. Someone like Griezman or Auba is a dream but it could happen.