Fortunately or not, history has shown time and time again that Parkinson's law still holds - work will always fill the allotted time. Pretty much the only way to decrease it is to mandate fewer working hours, like is starting to be done in Europe, for example.

If you want to work less you can do that. Many professional writers aren't regular W-2 employees but rather independent contractors paid on a piecework basis. They can use any writing tools, including ChatGPT, and can work as few hours as they like. Of course, prices will continue to fall for low-effort writing that doesn't involve any unique insight or original research. That was already happening with offshore outsourcing before ChatGPT was released.