I understand where you are coming from, but I hope you realize this is very subjective. The things you mentioned and other elements of the fantasy genre do not become irrelevant for many people through their life, well into adult life as well. In fact, they may become irrelevant and become relevant again.

Just to make it clear (and perhaps to state the obvious), you are not believing in these when you play these games or read these books, you are voluntarily suspending disbelief.