The LLM has its context-window. When it gets over that I assume it starts more or less repeating itself. Whereas human context-window has memories and inputs from all of one's life. Therefore great authors don't repeat themselves.

Now even if an LLM has a large context-window it is probabably not the case it rememebers all of your previous prompts and all of its previous replies. If you ask it to write a book you should probabaly give it all the previous 50 books (or blog-posts) it has written for you so far and you should tell it not to repeat itself. But in practice the context-window and the cost of token would become too expensive for it to write 50 unique books.

Maybe the problem is "all-or-nothing" -nature of LLM context window. Humans don't remmeber everything from past but they remember something from ALL OF their past.