Think Januzaj is more an attitude problem. Plus, I think he's rubbish.
In terms of showing trust, and I've said it before, if someone is good enough then it's hard to ignore them. If Lingard could find consistency in his finishing he'd be lethal.
Still don't want LvG next year....As much as I do like him and prefer him to Moyes
I am not fully with you here, but agree on certain points.
What I see in LVG way of developing young players is that LVG tries to develop the players a whole package. Compare to SAF, who distinctly opted to make use of the youngster best attributes first, then hopefully they fill out the other attributes! So under SAF, we tended to have youngster (not entirely true for bought young players like Ronaldo, Rooney, Pique, Pogba... where they are known for having all around good attributes) who flawed in some attribute and never filled out. (Some were able to to fill out and Co92 has more success than most).
Example of these flawed players: Welbeck cannot score consistently lack the edge of real striker. Cleverley's physically mentally weak. He has some weird but good technique. Also has a good sense of moving into good position but can't make anything out of it. Evans lacks of physical strength and arguably mental strength too, can't perform to his best without having a senior figure beside. Macheda knows how to score but lacks everything else... We have some current ones that seem to follow the trend in Januzaj, Wilson. Both have some/many stunning attributes, but at the same time their other attributes weren't up to standard in team/under managers who require all around skills.
There is no saying the above can't fill out in the future, just the idea to compare with LVG way below. Wes Brown, O'shea, Fletcher's abilities IMO are all around balanced and are success. They filled out quite well, and because their contest is simply better or bad luck that they couldn't get better.
LVG youth development is getting them fill out all around then push up to next level, rinse and repeat. He will come off as breaking what is supposed to be working, but that's the philosophy behind it. He wants the players to together reach a comprised level, then push the whole team improve again with it. So in a sense, some player has to tone down their bets attributes to improve their weakness to match their teammates and make a cohesive team. LVG wants to get the young players involves in first team (not particularly get play time), but to submerge in the culture/ philosophy. He would give young players play time occasionally with first team and see how the youngsters fare. Those who prove themselves would be more involved. Here the big difference is LVG doesn't want to field 11 youngsters/ or youngsters with underplayed/reserve players. That would make play U21 team in real completions, not first team! He wants to field few youngster at a time with first team starting XI so the youngsters have actual real first team football. Problem our first team and starting XI is no where near complete/ good enough.
In contrast, SAF first team experience is often being more about fielding U21 team in League Cup, FA Cup easier tie.Youngster made onto first team often have their weakness covered, carried by the senior players in hope the young players would one day fill out. Some did, some didn't. In SAF some players have to sacrifice more to cover for others to allow them to bring out their best attribute. By doing so, some players would suffer and stagnate their own progress. While some youngsters grow older but couldn't grow up their game and couldn't perform as well when the the senior players not around. There is no right wrong here though. Not entirely fault of either the player or the managers for him to not develop as expected. Just different managers have different ways/ philosophy. I myself prefer LVG's way in case we have an established team.
Mourinho is questionable when talking about bringing in load of youngsters onto the first team, but I can tell his method is similar to SAF's. Therefore fortune for some youngsters would term around quickly in a bad way or good way as he tends to make use of available best attribute than developing all around players