Campbell believed all stories were the Hero's Journey in some convoluted manner or another. Could tell him you tripped down the stairs, and he'd say something like, 'yes, but going down those stairs again would be you learning to conquor your fears, thus resulting in a more well rounded person.'

Or you could say 'I should stop drinking milk, because I'm somewhat intolerant' and he'd say, 'ahh, yes, you're in the middle of the hero's journey, on the precibus of learning to set your desires aside for the betterment of your health'

Any story with conflict becomes the hero's journey, and what stories worth telling don't have some kind of conflict. 'Proto-story' nonsense.