I think you’re giving Campbell way more credit than he is generally given by the writing community at large. Yes, that is one way to write a story, but it’s certainly not the only method taught. For example, slice-of-life stories are completely acceptable, however it is harder to get some of the nuance across to new writers. The hero’s journey is an easy starting point, that’s all. And I really don’t think Campbell was trying to say that’s how everything should be. He was making observations about what he already saw in popular western media.

I don’t understand your seeming conflation of advertising and art, which seems like a separate point from your criticism of Campbell. Advertising does not control art, nor vice versa. It makes more sense to look at things through the lens of money: art can be basically free to create (writing, drawing, street art are all pretty cheap). Anyone can do it. Now, something like making a film is not cheap. It can cost millions of dollars, and not many people have enough lying around to do so without getting a return on that investment. In other words, film has to make money. They know the hero’s journey will sell because it is easy for the average Westerner to digest and enjoy. So you see a lot more hero’s journey stories on the screen than you do in the wide world of books, which can afford to be more experimental or art-driven. Someone like Banksy isn’t worried about finding a rich buyer to recoup the cost of his stencils and paint. Would you agree?

Advertising is a different beast altogether, and I’m not sure why you would criticize it for not being art. It was never supposed to be that.