Ferguson's impact in Manchester united can never be comparable as he has left a very big record that might be very difficult for any coach to break in Manchester united. Manchester united pattern of football eventually changed after Ferguson's exit from Manchester united. They've been struggling from one coach to another but none has been able to break the dead luck that has besieged the club for some years now. I think Manchester united needs a coach that can have almost same coaching experience Ferguson had during his coaching career for the club.
United's management needs to do something very fast to aid Manchester united performance as the club might really be paving their way to relegation and it will be very sad that a reputable club that has recorded lots of success in England will peradventure drop to relegation due to poor performance.
It would be very difficult for any coach to attain the record of Sir Alex Ferguson at Manchester United, especially wih the way it's poorly run currently by the Glaziers, they make it very difficult for most of the coaches that came after Ferguson to succeed in their 2nd tenure, by refusing to provide enough funds to strength the team, they did it with Mourinho, Ole and currently Erik Ten Hag, since Ferguson's departure the only coach that's almost break the dead luck was Jose Mourinho who finished 2nd position.
However upon the arrival of Sir Jim Ratcliffe to take over the sporting affairs of the club and the departure of several incompetent executives have left the club maybe we could witness a reformation in the team before the end of this season they could probably go back to winning ways.