I have also found that LLMs do not help me communicate my ideas in any way because the bottleneck is getting the ideas out of my head and into the prompt in the first place, but I will disagree with the idea that the output beyond the prompt contains no useful information.

In the article you linked the output he is complaining about probably had a prompt like this: "What are the downsides of using Euler angles for rotation representation in robotics? Please provide a bulleted list and suggest alternatives." The LLM expanded on it based on its knowledge of the domain or based on a search tool (or both). Charitably, the student looked it over and thought through the information and decided it was good (or possibly tweaked around the edges) and then sent it over - though in practice they probably just assumed it was correct and didn't check it.

For writing an essay like "I would rather read the prompt" LLMs don't seem like they would speed up the process much, but for something that involves synthesizing or summarizing information LLMs definitely can generate you a useful essay (though at least at the moment the default system prompts generate something distinctively bland and awful).