Artist's have _always_ been willing to take credit for their own work. We know of plenty of authors prior to the last few hundred years: Livy, Homer, Aquinas, you name it. The fact that some authors opened their work by honouring their muse, or inspiration, has nothing to do with them taking credit for their own work. Some of them, certainly not all, worked in the tradition of honouring the inspiration, but they still took credit for their work. Otherwise, how would we know who wrote what.
The only exception is author's who wrote in culture's that pre-date writing, or did not have reasonable access to writing, such as the Beowulf poet, or the Green Knight poet. Even then, I'm sure the only reason authorship wasn't recorded was because those that orally passed on the story, excluded the original author's credits.