Well - I agree with you to a certain extent - but not completely.
LvG wasn't particularly brave here - he just didn't have much of an option due to injuries. As for giving the Ajax-team a chance at young age - with all due respect to our youngsters, that was a one-in-a-million generation at the same level as our Class of 92. And in Holland you can afford to give them the chance at a younger age because the football is less physical and the opposition is much weaker.
At the same time - Ferguson gave very few youngsters the chance before they turned 19:
Scholes made his breakthrough around the time he turned 20. Butt just before he turned 20. Gary Neville made his breakthrough about the time he turned 19. Beckham and O'Shea had turned 20. Phil Neville and Wes Brown just after they turned 19. There were exceptions like Giggs - but they were few and far between
Please feel free to disagree.
Van Gaal at Ajax brought through teenagers into the mens game in the Eredivisie which was stronger than the Eredivisie today IMO. The Dutch are also said to be amongst the tallest people on earth with the average male standing at 182.5 cm. So physically the Dutch were always strong but the difference was that they were also technically and tactically ahead of the game.
Yes the Dutch did have a brilliant batch of youngsters coming through. But if it wasn't for 39 year old rookie LVG, we would never have known that, because when he brought several kids through to the first team, many in Holland said he had lost the plot and needed stopping before he did any more damage. Bergkamp had recently left to test himself in the best league in the world at the time and instead of using the proceeds to buy players externally, he decided to use the resources at his disposal and took the decision to promote from within with spectacular results, playing a possession based style which was turbo charged with modern concepts for the time, which were straight from the Rinus Michels' total football play-book. We also know now that LVG didn't care if the player was young or established in the game as long as the said player understood his concept on the pitch. And it was said by many that LVG preferred coaching the younger players because it was felt the young players were more willing to learn his concepts rather than say a superstar player.
Van Gaal also gave opportunities to many young players at United which I was critical of because I didn't think the likes of Blackett, McNnair etc were ever good enough. And he brought through Marcus Rashford straight from the u18s to the first team which was a typical LVG move with or without injuries. Because I don't believe any other first team coach would've done that. But the key thing to note is that LVG was not afraid to make the big call with younger players even under immense media scrutiny even when he was a rookie with no track record as a first team coach.
Fergie brought Giggs through at 17 which wasn't a surprise because he was the best youth player at the club according to many. Scholes was a striker coming through and he had a number of very good players infront of him, So Fergie had to make a big decision, which meant, out went established winners like Hughes, Kanchelskis and Ince and were replaced internally by youngsters like Scholes, Beckham and a external signing from Forest (Roy Keane). If there was social media at the time, there would've been extreme melt downs which would've been exacerbated after the 'you can't win any thing with kids' game, which we lost on the opening day of the season.
The point is that Fergie and LVG made big calls and were prepared to back multiple young players against popular opinion. And they weren't afraid to do that even if it meant they lost a few games.
