Pique and Pogba not enough? Welbeck is a starter for England.
Not getting a game because you're stuck behind world class talent or if the manager wants to ease you in is different than not producing the talent in the first place.
It's a bit of a stretch to say we produced Pique or Pogba.
Pogba we spotted as a very talented 16 year old and he left less than 3 years later as a very talented 19 year old. You either have to credit Juventus with turning him into a top class player or his former clubs for his development as a teenager. He didn't really even feature in our first team, which is where most of the actual development occurs, playing against top class players.
Pique we signed as a very talented 17 year old and he left as a very talented 20 year old. Likewise he barely featured in our first team and most of his actual development occurred at Barcelona. Zaragoza should get more credit for his development than United.
However I agree with your general point: Depay has a far greater chance of succeeding vs Januzaj as he's actually played competitive first team Football for the last 3.5 years.
The club cant simply lose touch with the entire local community and that's what would happen if they simply shut down the academy. Also, it isnt just about players making it into the starting 11, squad players and even players sold for good fees to other clubs. We can't buy 25 man squads.
Not training youngsters has no big relation to losing touch with the local community. We'd still do local charitable work, we'd still support local work and we'd still contribute to the local community. We just wouldn't train youngsters.
Of course we can buy a 25 man squad. We'd have 3 "kinds" of players. Younger players who are either spectacular for their age and can contribute as squad players or are good for their age and will be bought and instantly loaned to clubs where they are guaranteed first team Football. Then you have players who have progressed from the aforementioned category and become valuable first team players. Finally players who have been bought for huge fee's in their prime and have slotted straight into the first team.
The only difference between our current squad and this squad would be that our younger players would have first team experience when filling squad roles; rather than the current situation where they are playing what amounts to a different sport the quality is that poor.
We'd have a totally different model where we'd be buying 5-6 talented youngsters for the £5-10m price range every season from across the globe and loaning them out straight away to clubs who'll guarantee them first team Football. Once they were good enough to fill a squad role they'd fill said role.
It's no different to the Chelsea model now. They buy the best young players and loan them out. However I'd definitely give the likes of De Bruyne or Lukaku etc a chance before shipping them off for a profit...