LLMs are good at writing long pages of meaningless words. If you have a number of pages to turn in with your writing assignment and you've only written 3 sentences they will help you produce a low quality result that will pass the requirements.

Low-quality is relative. LLMs' low-quality is most people's above-average. The fact the copy - either way - is likely to go through some sort of copy-by-committee process makes the case for LLMs even stronger (i.e., why waste your time). Not always, but quite often.