LLMs can generate content but not really write, out of the box they tend to be quote verbose and generate a lot of proforma content. Perhaps with the right kind of prompts, a lot of editing and reviews, you can get them to good, but at the point it is almost same as writing it yourself.
It is a hard choice between lower quality documentation (AI slop?) or it being lightly or fully undocumented. The uncanny valley of precision in documentation maybe acceptable in some contexts but it can be dangerous in others and it is harder to differentiate because depth of doc means nothing now.
Over time we find ourselves skipping LLM generated documentation just like any other AI slop. The value/emphasis placed on reading documentation erodes that finding good documentation becomes harder like other online content today and get devalued.