I think his development has been slowed because Bailey has tried to make him accountable for an opponent thereby asking him to win contests.
He struggles to win contests because:
A He is not physically strong enough.
B Because of A he doesn't have the confidence in his body.
C He possesses a slow reaction time and struggles to take the correct option under pressure.
I do agree that Morton's survival as an AFL footballer is dependent on him owning a role. I cannot see that role being as a midfielder and he will need to become physically MUCH stronger to play as a flanker at either end.
Unfortunately not playing Morton as a midfielder neutralises to an extent his greatest asset which is his running ability.
At the moment Morton is a weak bodied mid, with slow reflexes and average disposal, so he and the club need to look at what they can do with him whollistically and adopt a whole new training regime IMO. I have no doubt that the club knows all of this better than we do.