Fitting The Story of King Midas into the 12 steps of The Hero's Journey is basically asking for a headache. Sure, some of the steps fit, but it would require a decent bit of stretching, and let's be honest: we're not that flexible.
So why doesn't it fit the mold? Because the story of King Midas isn't intended as a hero myth. Instead, it's a parable about the dangers of greed. What can we say? Not everyone's meant to be a hero.