At what point (if at all) do retellings become original works?

Hi all, I hope everybody is well! I’m currently in the planning stages of writing my debut novel which was initially inspired by the Orpheus X Eurydice tale. However, I’ve basically changed everything except for the main motivation which is to “go to the underworld to save someone you love.”

For added context, the entire journey through the afterlife is completely different and the vibe will be more of a Gothic Romance than centered around Greek Mythology.

Do I still call it a retelling at this point or do I say it was influenced by the tale instead?

It’s still a long way to go until I’m querying or anything but it keeps niggling at me so I’d like to just lay it to rest.

Thank you for your help!