Yes, the term technically include book authors, artists and others as well, but those people don’t normally call themselves content creator. In fact I think that highlights the difference between the mindset: the “content creator” is all about pumping out quantity of content, quality be damned.
All of this is just a long way of saying that the decreased income security for “content creator” is less about the ability of ChatGPT, and more on the uselessness of a lot of “content” out there.