It’s even more stark the further back you go. When the printing press was invented, it didn’t usher in a new era of creativity but instead the first few centuries resembled modern Hollywood: shameless sequels and reboots. By far the most popular books were translations of Greek classics and rote derivatives of the Arthurian legends. It wasn’t until the first iterations of copyright and a few other cultural shifts that a “professional” writer class was born and started to expand on the creativity of our stories. Until then publishing wasn’t profitable enough to support a real creative process, so they cribbed as much from existing canon as they could to make ends meet. See how long it took science fiction to properly develop into a literary form, for example.