Suspension of disbelief is a real thing.

They could've written in a unicorn that pisses refined gasoline and it would've made more sense than spending the whole time portraying "realistic survival techniques from a doomsday prepper" that don't add up at all.

It's the same problem people had in Game of Thrones in the last seasons where time didn't make any sense. A crow flies halfway across the continent and Dany comes to their rescue on dragonback overnight? If you're going to set up rules for your made up fantasy universe, you still need to follow those rules or it doesn't work.