Just a couple of days ago, a customer rep at a company we partner with dropped a long doc that had basic reasoning errors once you got into the individual sections.
I would have much preferred if the rep had written a shorter document and reached out about things they were uncertain about. Instead thet wasted my and my team's time as we first tried to make sense of the document on good faith before realizing the problem.
I don't care if people use LLMs per se, but if this is functionally the result, then in this aspect of my work things would go much better if people did not use them. They are a great interface for talking to a machine, but due to the laziness they breed, they are a terrible interface for talking to other humans unless approached with a great deal of discipline.
Yes, you hit on the main problem with LLMs for writing. It doesn't cost you anything. It can do the reasoning for you and creating long messaging with dodgy reasoning.
I think you should write down your thoughts, tell it to make the points you spelled out and be concise and respectful of the reader's time and attention. When I do this, it works very well. But I agree if you just have it respond and reason it tends to often produces bad responses.