Imagine a chef, congenitally unable to taste or smell food, who has nevertheless studied a million recipes. Can they reproduce existing recipes? Sure, if they follow the instructions perfectly. Can they improvise original recipes? I doubt it. Judging by the instructions alone, the recipes they invent may be indistinguishable from real recipes, but this chef can never actually try their food to see if it tastes good. The only safe flavour combinations are the ones they reuse. This is a chef who cannot create.
LLMs are structurally banal. The only plausible route to a machine which can competently produce original art requires the development of a machine which can accurately model human's aesthetic sensibilities—something which humans themselves cannot do and have no need for, since we already have those aesthetic sensibilities built in.
This is the fundamental error of using an LLM as a ghostwriter. Humans don't only bring inspiration to the table—they also bring the aesthetic judgement which shapes the final product. Sentences written by an LLM are banal sentences, no matter how you prompt it.