There's a line between showboating versus experimenting. Most tricks are not fundamental skills, and there's a case to be made for stressing the latter at a young age in order to develop good technique, muscle memory, etc. A young player should not be constantly trying new things like he saw in a Champion's League highlight or playing FIFA video games. Then he/she is just screwing around. But coaches need to recognize that kids need to enjoy the game, and they need to be free to try things. It always amazed me how many coaches and parents at youth soccer games thought that making a mistake was a terrible thing, even though most of them would acknowledge that in most areas of life, making mistakes are how you learn. The example I used--passing with the outside of the boot--isn't even really a "trick." It's a recognized skill and many coaching materials and resources teach how to do it well. Many famous players are known for being particularly good at it (my son idolized Isco when he was young). His coach wasn't yelling at him for trying to something flashy and unnecessary, he for some reason didn't want his players learning a skill which is admittedly harder but not at all superfluous.