Ok speculation time...
A vast realm beloved by the gods since time immemorial.
So a vast realm would probably mean this is a/the major continent on the planet. Being beloved by the gods suggests that Eorzea is a place with abundance and general peace. So perhaps other areas have climate/monster/beastmen problems being that they are not blessed?
All save its name stands lost to the ages.
This would suggest that the world's inhabitants have forgotten much about this place. We've seen something like this before in FFT. Remember the airship and gun explanation in FFT?
MUSTADIO: Know why my friends and I are called "mechanics"?
[Ramza shakes his head.]
AGRIAS: It's said that a lost civilization lays hidden under the city of
Goug... In St. Ajora's days, countless airships sailed the skies and
fantastic machines walked the streets of men. But time passed, technology was
lost, thus none know whether such wondrous things ever existed.
MUSTADIO: But they must have! Hundreds of airships and exotic machines have
been excavated from under Goug. We mechanics do our best to restore these
legacies from Ajora's time.
So perhaps the people were advanced with a working knowledge of machinery but civilization collapsed, plunging things into a midevil-esque situation where the people attempt to operate and recreate old technology.
Just some speculation. Your thoughts?