All good fantasy writers do proper world building and lay out their own internal rules either through exposition dumps or by showing an action and the consequences of that action. It's hard to do too much pure exposition in a comic because of the limited page count, but also because so much of the story is imparted through the art as well as through the characters' words and editorial comments. Marvel does its best. They have made writer guidelines before (referenced here in this thread) but the problem happens when writers just use the characters to do some badass hand-wavy stuff to score a plot point of some kind. Pretty soon you end up with all of the magic users being interchangeable. If a writer just wants to use any random magic user in their story, pretty soon it seems like all the magic users can fly, turn invisible, teleport, travel in alternate dimensions. have cool magical laser beam hands, read minds, fight gods, etc. Every writer wants their character to be the most powerful at whatever they do, in the context of the story they're writing, even if amping up a character in one story might not make sense for the character overall. It gets to be an annoying mess, so I understand your interest in having Marvel lay out some rules and guidance on who can do what. It's a good idea, so long as you understand that not all of the magic users are the same. Strange has different skills and abilities from Wanda who in turn has access to a different level of magical energy than Agatha, but who lacks Agatha's centuries of study and mastery, etc.
Who knows? Now that Marvel has made Strange such a prominent character in this current phase of the MCU, perhaps they'll come out with an updated Marvel Tarot or some other sort of guide to the Marvel magical universe that will provide a framework for their writers and the fans.