Why do people have an issue with this world being a stage/simulation?

Have you been on Pirates of The Caribbean, in Disney World? They have a fake sky. It's a whole world under an artificial dome.

Imagine a Pirates of the Caribbean world built by an alien civilization, just on a scale 1,000,000 times bigger than the Disney one. Why is that so hard to imagine? My gut tells me this world is a collaboration between Orion and Sirius. But don't quote me on that.

*

Alternatively, imagine a kid born inside Pirates of the Caribbean. Everyone conspires (under penalty of fining, imprisonment or death) to not tell the kid that there's an offstage world.

What would happen?

~O~