You focus too much on derivative generation. Yes, LLMs can do that, they can paraphrase texts, restyle them, summarize. But usually we provide 10 or even 50 different sources for the model to extract an answer. So it does something on top, it correlates information across sources. Synthesizing from 1 source could be derivative, synthesizing from 10 sources is meta-analysis, something new. Another reason we don't generate derivative content is because we actually don't need to do that, we need direct answers to our own questions, not to generate a clone of a book or article.