Just now it will be tough for any young player, those just coming in from outside like Yoro; or coming up through the ranks, and in having to change playing positions, style, etc. and being alongside a number of more senior players, many of whom won't be here a season from now.
All this is taking place in what is a poor season already, that might get better but equally might get worse. It will be a 'baptism of fire' for all the youngsters, but also a unique opportunity to take /make major advancements in their careers, fairly quickly. Just how many will survive getting 'thrown in at the deep end', it will remain to be seen, but one thing for sure those who do survive will become the 'bed-rock' players in the new style Manchester United.
On the bright side the new manager knows what he wants and seems to be prepared to push on towards it, despite all the noise around the club. How long it will take to get to where Ruben wants to be is hard to predict. What shouldn't be hard to predict is how he wants to play, the kind of players, most of whom will likely be in the age range 21-24, he wants, and the levels of fitness he will demand to go along with the technical skills required.
From his interview with Rio it sounds as if Yoro has a good idea of what he has let himself in for and intends to see it through.