I think the problem with the premise is that, even though young players have raised their collective value in the regular season, the game changes in the playoffs, and, a lot of times, they either wilt or take a backseat to a more experienced teammate.
Cup winners in recent years really haven't been led by 21-23 year-olds the way the regular season teams have been. Your best playoff performers still seem to be in the 25-32 bracket, probably because clutching and grabbing become more acceptable, and, just like in the 90s and early 2000s, suddenly experience becomes a big deal to work through all the BS. But, if the goal is winning the cup, some of these guys oozing talent are gonna have to show what they can do when it counts before taking all their team's money.