Like I mentioned before, I have watched him closely and I don't rate his potential very highly. Even if he is still a very good pure goalscorer (possible, but also unlikely - he didn't do that well at Euros ) I am afraid he has reached his ceiling due to some natural limitations to his game.
I can be wrong here, but it really seems people talk about potential because of his age rather that actually explaining what specific elements of it. Same happened last season to Antony, plenty of people shouting about his potential. They are not on the same level at all, but you get my point. He's getting a lot of leeway because of his age, that's fair, but that's not a particularly interesting discussion as far as "let's give him time" kind of final statement goes. I'd prefer to talk about specifics.
You are not the only one, pretty much most United fans here watched all his games this season
Some also watched him at Atalanta
He should be getting a lot of leeway because of his age
What do you specifically want him to improve specifically? There is plenty he will and can improve on, but most of all, he will be more accustomed to the pace and speed of play in the PL; also, hopefully, the team as a whole will improve its play because this hurt him this season.
The major issue I see with him is that he needs to become a lot better in the air; for someone for his size and physicality, he is surprisingly poor there, and he also needs to stop engaging defenders in physical battles over getting hold of the ball (a lot of this is just experience)
If you watched him at Atalanta, you would see that he is actually very good at working the channels and isolating defenders 1 vs 1 (something we didn't take advantage of at United), things like timing of movement etc comes with understanding his team mates better because the attack last season was abysmal
For a striker, though he has the one attribute that you can't teach, he is a very good finisher with both feet.