Except that everything in the series is different from our world. In “Raiders” , the Ark was “one thing that’s different from our own world,” but then the stones in “Temple” make it two, then the Grail in “Crusade” makes it three. And along the way, we get priests who can magically remove your still-beating heart, 500-year-old knights, yadda yadda. Obviously, Indy doesn’t live in anything close to our world.
And I’m not sure that’s a good thing, really. “Raiders” works because for most of the film we think Indy does live in our own world, and that it’s a movie about a fists-and-bullets adventurer, not ghosts or angels. The notion of the Ark of the Covenant being a real thing – real in the sense that it actually provides a connection to the Almighty – starts out as a far-out, ridiculous concept to Indy, the government men and basically everyone except nutty old Adolph, but as Indy and Nazis race to find it and progressively stranger things happen (like the swastika spontaneously burning off the crate), real suspense grows, until when the lid comes off and all Hell breaks loose (literally), we’re left to go, “Holy Crap, it’s the real deal!” An old-time serial takes a left turn into supernatural horror, and it’s a clever idea.
The problem is there’s nowhere left to go after that. After a brush with God, you can’t follow up with adventures that are down-to-Earth. Indy can’t just fight standard, Earth-bound Nazi plots in the sequels. We thought he might have a more Earth-bound adventure with “Temple,” seeing as how it was a “prequel” set before his brush with Divine Wrath, but no, that one had those goofy power stones, or whatever. So now the Ark isn’t even Indy’s first brush with the supernatural; it’s just another day at the office.
Four films in, we have a character who lives in a world where it’s all real, every myth from every culture: avenging angels, immortal guardians, chalices that grant immortality, voodoo curses, flying saucers buried in jungles. Indy goes from an old-time serial hero having real-world adventures to Fox Mulder with a hat. Like an M Knight Shamalan movie, we can never be surprised again; from the first frame, we’re thinking, “okay, what’s the ‘impossible’ phenomenon this time?”
In other words, I don’t agree having supernatural elements in the first 3 Indys makes a Sci-Fi twist unworkable in “Skull,” because the brakes came off a long time ago. Basically, anything is possible in an Indiana Jones film, which makes them wonderful and pointless at the same time. If they want to end the next movie by transferring his consciousness into Chris Pratt through a magic spell, how can we cry foul? We’ve swallowed everything else.