If Van Gaal had succeeded then you probably wouldn't be making this point, to be honest.
Bad decisions isn't necessarily sign of structural incompetence. On paper, allowing Ferguson and Charlton the chance to make decisions made sense. Football men, great experience, knowledgeable etc, etc. I don't necessarily agree with that premise myself, but it's a worthy point. It works at Bayern, for example.
Appointing Van Gaal made sense at the time, too. It simply hasn't worked out under him because the football hasn't been good enough, not because of the Glazers or Ed Woodward. The noises around the club seem to indicate a lot of structural change within the club, anyway. Academy, scouting network, a possible sporting director of some sort? I think we'll be quite alright.