I think the same. If they're not in and around the first team at the age of 20-21, you've got to think are they at the right level.
Hackney (21) is the same age as Terrell Agyemang
VDB (19) is the same age as George McCormick, and younger than Jack Hannah
Coburn (21) is a year younger than Gilbert (22)
Thomas, Greenwood, Gilbert and Hoppe are 22 now and should be looking to be playing first team football.
Players develop at different ages and stages and yes Vardy signed for Leicester when he was 25 but i think if you're looking at the law of averages then if you're 20/21yr old having come through the academy where multiple coaches have seen you, seen your progression and you're not anywhere near the first team then chances are it isn't going to happen for you here. Nothing to say they can't go on to have good careers as professional footballers elsewhere though. The club will know who in their mind can step up and who can't, so its their job to push them into the view of other clubs now who can come in and buy them from us.