He'll bloom once he overcomes his niggling injuries and starts coping physically better.
Dunno why so many want obviously talented quite young player sold at the drop of a hat.
To be fair, unless you watched him much in the youth teams, there is nothing 'obvious' at all about his talent.
For me there's two sides, it's not good practice to just 'write off' young players as you put it, but you should also not just stockpile them for years either. Wilson is just 20, but he's been out of the reserves for 2 years now. That in itself isn't necessarily THAT long, but in that time, he's generally been poor for us too, which does add context. If he'd shown more, even out on loan, it would be different. Take Januzaj. He's still on our books, and has underwhelmed both here and on loan for two seasons, however - he HAS also shown in our first team for a spell of games that he can do it at THIS level, not just youth level. Wilson has not, which is he key difference.
We also have the likes of Will Keane around still. It is highly unlikely he'll ever be a United player. Just let him go. He's 23. Players are on their second World Cup by then, some approaching their third. I heard talk today about loaning Jones out even. Since when did teams start loaning out 24 and 23 year olds? It's unnecessary stock piling I think.