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.
Quite. Its the attention economy, you've demanded people's attention, and then you shove crap that even you didn't spend time reading in their face.
Even if you're using it as an editor... you know that editors vary in quality, right? You wouldn't accept a random editor just because they're cheap or free. Prose has a lot in it, not just syntax, spelling and semantics, but style, tone, depth... and you'd want competent feedback on all of that. Ideally insightful feedback. Unless you yourself don't care about your craft.
But perhaps you don't care about your craft. And if that's the case... why should anyone else care or waste their time on it?