Not sure I get your point.I agree with you but its not always the case. Lions premiership years we had Shattock, Hadley, Cupido, Headland and McLaren off the top of my head. I think they all were highly rated youngsters.
Cupido was a very exciting young player who I thought developed nicely. He kicked 40 goals in his 3rd year (at Essendon by then) Struck down with injury, he never recovered form at Essendon. Either clubs' fault, or just Damian?
Shattock was a premiership player, proving another argument that you don't have to be super to contribute.
All highly rated, and Headland in particular developed well here and failed when he left. I think those examples show flaws in highly rated players, not a failure to develop in a good team.
Those examples you gave prove the point somewhat because they looked good here (at times, some more than others) but failed at their new clubs. Headland for example was a #1 pick and looked like it here. At an average Fremantle, he failed.
My point was that the kid who is directed by an experienced team on game day and hit up with clean disposal as well as good players adjusting to receive average disposals will look and play better than the same guy forced to play with 10 others just like him. Then there are the ones who just don't make it.
Have a look how many times people have complained about one of our youngsters being "robbed of a rising star nomination, sometimes by an average type. That average type playing in a better team looks better and sometimes does better, because of the team around him.