This is the opposite of what I see in reality right now. The hard part is to make the artists do exactly what you want, down to the subtle but meaningful details. That happens because the high-level instructions don't have enough capacity to deliver the full meaning. This is the same with generative models: extremely hard to control with the "prompt engineering" gimmick, it's only fine when you are OK with random output. Besides, they are purely functional and lack feedback mechanisms the creative director usually employ with artists.
That's why people are trying to make techniques more complex - large animation houses experiment with training their own model architectures and software. This is the way 3D CGI was born - simple at first, and yes it got plenty of doomposting at first (we are getting replaced by computers!), until it was clear that the field becomes extremely technical and complex, so it even has dozens of specializations inside it.
All entertainment is ultimately based on novelty, as human brain is really good at distilling meaning from the ocean of information. If you start with little meaning (your example - "a cowboy with blue skin with a laser cannon riding a unicycle through the grand canyon with a dwarf chasing him"), people get bored - no matter how much randomized artsy-looking stuff you add around it.
If you think that AI can generate all meaning that is relevant to people, I don't buy it, as it doesn't have the same training material. It's trained on the result and is forced to reverse engineer what moves people; reverse engineering is a fundamentally more costly and opaque task.