You guys are completely overlooking Dek’s argument. He’s not saying simply that it the Last Crusade wasn’t meant to have a sequel, but that the film was explicitly designed to preclude the plausibility of a sequel. While you can say the former about Star Wars, you cannot say the latter. Very different arguments.
Actually, you can definitely say that about Return of the Jedi.
EDIT: Frink beat me to it.
And I think it works perfectly well for ROTJ. I don’t care for the existence of any Star Wars films after that.