If United were only interested in signing boy scouts then we would have missed upon talent such as Cantona, Ince, Robson, Yorke, Keane and Co.
Sancho had proved to be quite mature by leaving the comfort of his home and risk everything at Dortmund. Sure he made mistakes as well. However we are talking about a 20 year old here. He's no Balotelli, Gazza or Cassano
I believe that one of United's many problems is down to the fact that we have too many boy scouts. We've got too many 'club ambassadors' in all but name who are just comfortable with us losing matches. That's why someone like Bruno Fernandes whose renowned for smashing lockers after losing a game has become so popular at the club.