All managers make mistakes and errors in judgement. Of course even Ferguson couldn't be right about everything. However, being able to create winning teams, handling players and winning trophies throughout, given how much the game and the football industry changed in his time is nothing short of extraordinary.
Since the club did nothing but appoint a new manager when he left, they were bound to end up in trouble. Unfortunately, it seems they are thinking about restructuring their club model towards a more modern setup. But they are still a few steps away from being anywhere near the powerhouse they once were, and probably never will be again. Remember, it took them 26 years to win their next championship post Busby, we'll see how long it takes this time around.
Changing the culture at a club is extremely difficult (we saw that with when Levy initially started), even more so when the club with built around a personality.
United might be trying to change things, but the Solskjaer appointment is proof they really haven't thought it out (if he hadn't played for them, his name wouldn't be on a top 500 list), the he's only caretaker, then a day later, well he could be in running for job, etc. shows they fired Jose and they still have to figure out plan B.
Funny how they are the biggest club in the world, but they can't actually seem to get the biggest managerial names in the world (Moyes, has been LVG, Jose after his disaster time, now a young an upcoming Spurs manager?)