It's not just about having the resources. If the talent of the graduates equated the money pumped in, teams would be pumping loads of their cash into their youth setup knowing that a couple of years later they'd be producing world beaters the likes of which they could never afford. Producing top-class youths is about so much more - the coaches, the organisation of the club, the style of play, but also the level of competition, the size of area recruited from, the culture of the players, the competitiveness of the games they play.
With the best will in the world, football is not one of those "do something 10,000 times and you become an expert" things - some people are just born naturally gifted at football and some are born destined to never be good enough, and you have to get lucky first of all and recruit someone with the ability to make it at the top - and it's not just about identifying the best young talent: I could name dozens of players who excelled at youth level and then struggled to even make it as a professional, while the likes of Jamie Vardy show that some players written off from a young age are actually extremely capable late-bloomers.
On top of that, you could have the next Messi but if he isn't playing teams better than his own he could turn out to just be an average second division player at 30 - in all sports you have to play someone better than you in order to learn from them, and competitive matches are all-important. If we dominate US academy football for decades it could all come to naught if the other teams are so bang average that they offer no growth for our own youths. This is, of course, why NYCFC is sending their kids off to Bolivia and Spain, but those are only one-off events and we need a continually high level of opposition.
In fewer words - you need the right conditions. Don't just assume that because our first-year guys are doing well it means we have the next Class of 92.