Well the arms have fallen off most of the young pitchers...
Being serious though, obviously Dusty will do what he thinks gives his team the best chance of winning so I think it's unfair to say Dusty won't play youngsters. It's just that he tends to overvalue experience and will give veterans long leashes even when slumping badly.
Here's some questions in answer to your question-what youngsters has Dusty managed to greatness? Also, what's a FO that just signed Dusty more likely to do (especially if his opinion about the roster are considered), funnel him youngsters or find a way to get him what he historically has preferred the most?