That makes it a derivative work
No, and this is well established in copyright law. You can write a story with elves, orcs, goblins, trolls and so on and the Tokien estate can't come after you. Many have. In fact there's a whole movie sub-industry that is built on skirting as close to legal infringement as possible, and it's not going anywhere: https://en.wikipedia.org/wiki/...
Further the person who takes a photograph of a famous painting owns copyright on that photograph. The creator of an audiobook owns copyrights on that audiobook, although if made without permission the writer may have grounds to pursue for damages. http://www.mediamusicnow.co.uk...
Then there's the problem of orphan works. If in 10 years your there is suddenly a demand for reproductions of your post and Intrepid imaginaut can't be located, how does keeping it locked up benefit either you or the potential audience for your work?
Well no system is perfect. I support creative people who put their work into the public domain and condemn things like criminal sentencing for non-profit sharing, and especially attempts to extend the meaning of "derivative", but I'm not seeing any reduction in artistic endeavours over the last few decades. Quite the opposite.
Instead we're moving slowly but surely towards a regime of unending copyrights with no public domain.
Again though, does that hinder or inspire creativity?