When Jurgen says he wants the youth to push through, he means to actually push to be in the 11, not to ride the bench, that's not pushing through. You bring up Miazga, but in no way should he be considered with his lack of game time since his move to Chelsea. You can't ride the bench on your club, and then expect to play for the national team.
The national side is in bad shape, partly because of poor coaching, and then a general lack of talent with the aging vets declining and the young youth not having the ability of the previous crop. I don't see many players that can develop into what Donovan or Dempsey were in their prime. That's a problem. Then the guys with real potential make poor career decisions and go to clubs way too big for them.
At the end of the day, the national side should not be a development ground, even though that has been the belief lately. The development value a young player gets from playing some random national games or some trainings with Jurgen are minimal at best. The national side simply needs to field the best possible senior squad available to them at that very moment.