Because in my opinion in terms of natural ability you are talking about potentially the best young player I have seen come through at the club. Left foot, right foot, pace, balance, step overs......I would from what i have seen put him aboe the likes of Morrison, Pogba in more recent times and even ahead of the likes of Giggs, Scholes, Beckham....that is why it is unfair to compare in my opinion.
I am not sayign stop being mean, said myself pretty much he is a very talented yougster and naturally at that age a lot of rawness and mistakes in him, I dont think he is ready to start games.
Also no amount of talent means a dead cert. Greenwood was doign well, still feel his future at the time was as a 9 or 10 and he could well have gone on to have been one of the countries great strikers......but that wasnt a dead cert. Maybe it was knowing the off pitch problems, but his attitude, greediness and general performances though better than some of the other dross following were not guranteeing that future was going to come good. Also Garnacho isnt a forward anyway