For some reason over the years the word mythology has come to be synonymous in people's minds with fiction. This was never what it was meant to be. The word comes from mythos, Greek for story, particularly oral story tradition. It is important to understand what ancient storytelling was all about. In antiquity people did not relate facts in the we way we do. Only accountants and merchants wrote facts. There was no concept of accuracy in reporting. Stories were a mixture of characters real and invented, sometimes several of these blended into one. Ordinary folk became giants, monsters, or even deities, and places may also have been real or imaginary, details of events embroidered, or completely fabricated. Heroism and adventure was the order of the day, and the message of the story was the important part, not the details. Symbolism was widely used, archetypal references to even more ancient events, places representing people and vice versa, and interpolation of politically expedient ideas. Also, with stories being passed on orally, people relied on memory, and details forgotten would simply be re-created from scratch. Neither the storyteller nor the listener expected the story to to be taken as fact, there was a far deeper truth involved, a moral tale perhaps, or an attempt at describing and explaining natural phenomena. This was poetry, not history.
Eventually of course humans taught themselves to write, and these tales started to be recorded permanently. Still within the mythological mindset however, claims were made of many of the stories being of divine origin, and certainly sacred mythologies form the basis of most of the world's religions. That they aren't literal fact does not make them any less valid, worthy, or interesting. In fact the symbolism, and the delicate nuances in the layers of meaning are what make them so fascinating and the object of study of countless people, many of them "non-believers".
What remains then is the assumptions behind the description of anything as mythological. Are you saying it is false, or are you addressing its special status, as something far more important than mere history. Because to me mythology is the real truth, even when it is entirely fictional.