I agree it takes players different timelines to develop. I just do not buy the notion that players can be ruined by rushed development, ie making them play in a league where they are not the best player on the ice at any given time. They don't lose the talent/offensive creativity that they were born with. Just like you cannot coach that into a player you cannot coach that out of a player.
Confidence is huge, and a young player playing in the NHL will go through lower lows than they would playing in an inferior league, but ultimately they will develop into the player they were always going to develop into.
The only time I would say rushed development could hurt a player is if they were clearly not physically or mentally ready to handle an NHL schedule, and suffered a career altering injury or off ice habit during those years.
Players that are essentially not good enough to be regular nhlers. Either yet, or ever.