You sort of have a point, since this is Disney we're considering, but this is a slippery slope.
Most _everything_ is derivative work.
Should I pirate all commercial software that's powered by open source software?
Should I never pay for a modern book with a hero's journey storyline simply because it's not original?
And I shouldn't pay artists for their covers or remixes of other songs? So unoriginal.
And why should I buy tickets to any new Batman movie? Batman's part of our culture and the story is probably taken from the comics.
And I should never profit from my business unless it's MY original idea.
If you dislike Disney (for good reason), then boycott them. But that doesn't give you the _right_ to pirate their content nor should you encourage others to pirate.