Age has a part to play where a child is considered incapable of making "correct" decisions and ultimately giving consent. There isn't some magical age where we mature overnight and become an adult, but for the purposes of legislation we say it's 18 (sometimes 16). When someone is capable of understanding and appreciating the implications of their decisions, they should be allowed to make them.

My age comment applies more to the "dictator" part than the "wasting good parenting" part, the latter is way too subjective.

Your use of misery is interesting. Children are miserable when they're told to do homework. This goes all the way until.... highschool? Some insight/foresight is required to see the true benefit of homework/learning, so I don't think immediate misery is a good indicator of what is good or bad parenting.