It's an interesting question to ask what Midjourney and OpenAI/Anthropic have that Stability and Google doesn't have. The best answer I can give is "good taste" - specifically the ability to take relatively standard model components/architectures and tune the hell out of them so that a lot of people will enjoy using the end product.

Having good taste is a hell of a moat, which is how fashion designers build multi-billion-dollar brands (I am not talking about the old "houses" - those are about the logo, but new brands are different), as well as chefs and visual artists. It's just a very different kind of moat than the one we expect as engineers.