The one thing I truly dislike about United's principles is keeping the players too long on the books.
Of course new signing might need 2, maximum 3 seasons to adapt and develop IF the question is in adaptation and the quirks of the league/competitions etc, BUT if player's mindset stays at the same low and won't show any progress, then why bother? Sell the player, get him off the books and buy a replacement who wants to wear the shirt and become the best. Mentality>skills. Talent without determination and motivation is nothing.
I am an entrepreneur myself and it's so hard for me to understand the board, as your "employees"/footballers are the ones who make the difference where it matters. And when you feel that they are half-arsed and lack the mindset, then you axe them. Not wait for 3+ years for some magical moment to happen. Like.... why? Time is so precious and limited resource.
It'd be so much easier to do that like we do hiring in "regular" life: hire, observe and when you feel that there's no fit, axe the employee and replace one. You don't give one 5 years and hope for the best. It's just so stupid approach.