I think one of United's biggest issues since Sir Alex started his decline was that United had been lead by the manager's ideology rather then what we need to do to return to our best. We saw Sir Alex refusing to deal with super agents and going full English proven talent which saw us not getting the likes of Moura, Hazard and co while losing the likes of Pogba for free. Then Moyes came in and went for the ridiculous (Fabregas etc) only to have to settle with his tall man from Everton and some player Chelsea wanted out. LVG stepped in and brought a horde of players to the club most of whom were either his own ex players (Valdes, Bastian) or Dutch players he fancied (Blind, Depay etc). Then Mou came in and brought in players who were either his former players (Matic, Lukaku) or had his mate Mino as their agent (Mkhitaryan, Ibra, Pogba etc).Finally we've got Ole who brought us back to the EPL proven players ideology which saw us blow 130m on 2 decent but hardly WC players. Leicester must be laughing their way to the bank as there's no way Maguire is worth 80m.
United need to bring in people at board level who understand football very well and can challenge the manager if needs be. There also need to be a certain criteria on how players are signed or who should be given contract extensions. For example CBs who aren't good in air shouldn't be signed in the EPL. Same with injury prone players (ex Bailly), players of a certain age (Sanchez, Matic, Bastian, Valdes, Falcao etc), wingers with zero pace (ex Mata) or players who simply don't want to be with us. The manager might sulk for months but certain red lines should never been crossed.