My main world (In my sig) is apparently 2.02GB, I say apparently as last time I uploaded it I'm sure it was around 1.35GB - but that's what it says in the folder right now. Being a 7 year old world though, some new things I have to travel extra, extra far to get/find whether that be by land/horse/donkey/boat or portal.
My main world is not as old as yours, but I have the same environment, with particular resources generating in further out areas that were generated under later updates. That situation does make for at least a diverse world, because in any world 'story', different regions have resources which justify a trade system. Otherwise pretty much everything that a player may want can be gotten with a short range.