I use AI to write documentation frequently. An AI agent, 600k tokens into a feature that it just authored, understands the feature as well or better than I do. It can document, compactly, what the code actually does, as well as the intent. These docs add value above having no docs and letting another AI, with zero context, read your bare code.
In the context in which I work, the quality of these docs is sufficient.
Unless your docs are being read by thousands of people, in 2026, in most contexts, handwriting docs adds less value than writing high quality instructions to your agent.
There are exceptions. For example, when kicking off a project, short crisp prose in a product brief aligns a team, removes uncertainty, and clarifies decisions. These are worth hand writing.