[Jensson]

Biggest effect is that your standards get higher. As a kid learning a game just meant learning to play it at a kids low skill level. Kids till spend years to get good. But as an adult who has played a lot of games you have gotten pretty good at many of them, then when you play a new game getting to that level again will take a lot of effort and time.

For example, you see the world records in factorio aren't held by kids. Kids has better reflexes which is crucial for some games, but their ability to learn isn't much higher than a young adults.