Do you continue to rotate player through the different positions as they get older? What is 'older'?
I have always made sure to give my players experiences in a number of different positions during the season. Sometimes in positions that they weren't well suited to but I wanted them to have a chance to play forward, for example. Moving the best players around the field is easier since you don't have to worry about exposing them to more pressure than they are capable of dealing with. By doing this there have been times that we lost games that we could have won if we would have played everyone in their strongest position. But if the most important job we have as youth coaches is player development, should it matter if our team loses because we were rotating players?
In competitive/premier teams in this area it's been my experience that coaches rarely rotate their players because thy don't want to risk losing a game. They are afraid that this might cause their players to tryout for the other team next summer. If it was only about helping players to improve then I think most coaches would agree that it's best to rotate their players. But when parents hold the purse strings then the coach has to keep them happy for fear of losing them. This is an unfortunate reality for most teams playing competitive soccer I'm afraid.
What can be done about it? I've always tried to educate the parents on my teams so that they understand why rotating positions is in the long term interest of their child even if it means that doing so will make it harder for us to win a game in the short term. Some have understood the rational and supported it while other couldn't get past the fact that this is 'competitive' soccer. They think this means that we should be doing everything we can to win the game. I believe that the players are still doing their best to win the game but now the kid that is always a defender is getting the chance to score the winning goal.
If we agree that players should rotate positions when they are younger, at what age is it appropriate, or even beneficial, to have kids play in positions that fit their strengths and benefit the team? I have usually waited to do this until they are 14 or 15, depending on the team. I still think there's a place for rotating players of this age because there is no telling where they might be asked to play for their high school or ODP team so wide range of experiences will help them adapt.
I'm sure Wayne Rooney didn't spend much time playing in the back as a youth player. There's also a case to be made for developing the specific skills needed for a certain position but I believe that the vast majority of our players are better served by having a broad range of experiences and skill sets.