I'm not saying your original works are fannish. My original works certainly aren't. And, good idea: don't post it to the archive; I'm not going to post my non-fannish original works there, either. No one will be making you post everyone you produce there, you know.

However, saying that no original work ever is a fanwork it's still asserting that the person saying it thinks their way to do fandom is the only way to do it. Because, surprise surprise, there are fandoms in which original works are posted and read alongside fanfic.