This is the problem that you're not understanding. You are attempting to remove the artist from the artwork and not understanding that one fundamentally feeds into the other. Brandon's internal journey from becoming a person who wants to write a novel to the person who writes Sanderson novels isn't some abstract thing that only he gets to appreciate. It's there, in his work. You can even see the change in his published works as his style and approach evolved over time.

You could craft an LLM to make the mountain of mediocre stuff that gets churned out, but the cost would be never having a great work ever again. No one would bother publishing if they couldn't get above the skill threshold that LLMs set, which would make the herculean effort that it already takes to write a novel to something positively sisyphean. And it's the job of making the whole novel that makes people capable of making the next great work.

And no, a prompt maker wouldn't be able to create a great work, since it's the marriage between your skill with words and prose with theme and narrative that makes something great. Since the prompt maker has no control over one, he could never master the other, nor ever hope to bring them together.