Dead Things and Not-Dead Dead Things
Skeletons and ghosts are different.
I just keep trying to see how the magically dead skeletons in Pirates of the Caribbean are the same as the rilly old (and thus actually dead) ghosts in Return of the King. Both of them are cursed, but they're really on the opposite ends of the spectrum - one set longing to live, the other longing for the peace of true death.
Both sets are traitors, but one set is an army and the other is band of pirates. Do they have a ton in common? Yes. But they also have several significant differences (on the shallow side - sickly green lights vs skeletons in moonlight). Not the least of which is the part where the Army ends up fighting on the side of our heroes.
Ultimately, it comes down to the fact that the Army of the Dead is dead and cursed to still linger, while the pirates are alive and cursed to feel dead.
I really should just start a 'pet peeves' list.