It's also fair to use it as a clever dictionary, to find the right expressions, or to use correct grammar and spelling. (This post could really use a round of corrections.)
But in the end, the message and the reasoning should be yours, and any facts that come from the LLM should be verified. Expecting people to read unverified machine output is rude.
I think we havent realized yet that most of us don't really have original thoughts. Even in creative industries the amount of plagiarism (or so called inspiration) is at all times high (and that's before LLMs were available).
An author that does nothing but "plagiarize" and regurgitate the ideas of others is incredibly valuable... if they exercise their human judgement and only regurgitate the most interesting and useful ideas, saving the rest of us the trouble of sifting through their sources.