There is absolutely a minimum size that doors need to be for almost any house. Yes you can incorrectly install other doors, but codes provide a minimum size for professionals to follow when installing. Which is 2.1m in most of the world. Other places will have their own standard size door, but yes every country absolutely has standard door sizes.
Why do you claim otherwise…? Just go look up any big box store door catalog lmfao, plenty of standard door options for even home owners. If you’re cutting a door to size, you’ve done fucked up in almost every case.
And it’s funny you say something like this while being completely off base about story heights… fucking lmfao. Sure we should listen to your “expertise” hahahah, you don’t even know how tall a room is, yet we should trust you know anything about doors? Really? Seriously… dude?