Have we? Mason Greenwood is as promising a player as I've seen at the club through the youth, and by many accounts, as promising as we've seen since the co92. And he looks to have a good head on his shoulders, unlike someone like Ravel Morrison. Of course hes young, but that doesnt mean he won't be a useful player. As it is, hes far more useful to us as a squad player than Sanchez is. That's nothing to do with imaginary expectations, that's entirely based on the 1.5 years if Sanchez and the little time Greenwood has spent in the first team. It's not even close in fact.
Anyway; what exactly are you arguing? Do you think Sanchez is a difference maker in any way? Do you think hes a useful squad player in any way? If so, what the feck have you been watching? Hes as useless to us as Darmian or Rojo are, plain and simple wasted wages. This isnt a case of Greenwood needing to be a key player, it's a case of all 3 of our promising young attackers being far better players then fecking Alexis Sanchez who is a sack of useless shit at this point.
As for Lukaku, his role in the team is being replaced by Martial and Rashford, and I'm confident both are capable of stepping up.