Agree with most of your post but I don’t buy into the above at all.... By the time they are in their 20s, no coach (including Ross) is going to impact greatly on the skill levels...
I personally think that could be the failing of a lot of footballers and managers. Thinking that they don’t have to do the basics anymore as they’ve made it.
Quinn became the player he did while at Sunderland because he trained everyday on his touch. He was playing head tennis with the rest of the squad and he was getting beat by the physios when he came here.
Obviously a bit of a light hearted gamble was what spurned him to improve his touch and by doing in constantly he improved.
There is a reason people say practice makes perfect.
The hardest part of a coach is training those often boring basic parts in a way that keeps the players engaged even at this level.