Your idea may not be new, and that’s OK
In any creative line of work (or, to be fair, any line of work or craft) a lot of people at certain moments in time can experience doubt about their output – that it’s derivative, not original, not good enough, people have already seen it, need to create something new. There were times when I have gone through this, I’ve seen other people experience this as well. I guess it’s only natural because we all want to leave a mark in the field we dedicate our careers to. A breakthrough, advancement in technology or design, something big. A ripple in the ocean.