Once you know what goes into these demos, it's not really comparable.
Can you ELI5 please?
I am guessing the user is referring to compute heavy nature of these demos to save on disk spwce
The demos are (a) an extraordinary amount of work and (b) rely on generative systems to produce a large world from small data, so it's usually not possible to fine-tune individual details of the world.
I think a “hello world” react project already has a bigger javascript bundle than this entire game, depending on how you measure it.