Well, it depends what you are trying to address.

Dota has a steep learning curve, which requires understanding and experience to learn.
The more you play, the more you understand and the more you improve your technique.

For young players, they may have the advantage of grasping things faster and have better reaction time, improving at a faster pace. But most of young players can be childish, like throwing the game if they cant get mid or do a lot of childish trash talking.

Older players learn slower, I have a friend who is in mid 20's fails to learn and grasp dota mechanics and tend to stick to one playstyle and play similar heroes only. Older players are most likely to behave better (like a sir) and not throw baby tantrums like younger players.

My 2 cents.