#2 Lack of leadership
For any team to be successful, they need to have a leader. That person should be someone who is well respected throughout the entire squad, including the manager and the staff, and needs to be devoted to the club. If we look at the squad during Ferguson's era, we can see many leaders such as Rio Ferdinand and Nemanja Vidic.
When comparing that to this season's squad, there is no identifiable leader in the team. Even though Ashley Young may be the only available candidate, you need to be consistent throughout the season, which Young is not.
Edited by Raunak J