I think you have a misunderstanding of what's copyrightable.

> This idea that they own the very idea of 'boy wizard who goes to school' is insane and plays right into this flawed and pernicious idea.

Copyright protects an expression of an idea, but not the idea itself. No one can legally stop you from writing your own story about a boy wizard who goes to school.

Nintendo fan games can be released (even sold) if they changed it up a bit so they're no longer associated with that IP.

> Copyright is important but does/should not extend to every time I want to print out a picture of a boy wizard for my kid.

You can. No one will sue you. No one will send you a cease and desist. It happens when you try to print Harry Potter and try to make a business out of it.