How has the empire not just obliterated the rest of the world?

[Corvanther]

Oh definately not a troll. It just seems it is on the level of a modern army in our world attacking a bunch of cave men, and losing. Basically what your saying is if the empire got its act together and worked as a team then the rest of the world would most likely be doomed.

[Rayo]

Eh less modern army vs cavemen and more Modern army against a High Fantasy Army
Also:

The Empire was purposely created by the Ascians to cause chaos. The Ascians needed a long lasting war to cause chaos and help further their goals. The dead really can't prolong a war but the living can. Now with the Ascians gone and Empire fracturing the individual legions are now actively trying to win the war rather than sit on their hands.

[Enkidoh]

Eh less modern army vs cavemen and more Modern army against a High Fantasy Army
Also:

The Empire was purposely created by the Ascians to cause chaos. The Ascians needed a long lasting war to cause chaos and help further their goals. The dead really can't prolong a war but the living can. Now with the Ascians gone and Empire fracturing the individual legions are now actively trying to win the war rather than sit on their hands.

^This. The Empire was

specifically designed by Emet to ultimately usher in a Calamity/Rejoining, and nothing else. That was his MO, find the most the put upon but ambitious nation, possess a lowly but important member of that civilization, invest himself into the upper echelons of that society, and then provide 'miraculous' ideas and technologies that turn that nation from an oppressed backwater into a war-mongering powerhouse, and then unleash them on the rest of the world, crushing opposition under the jackboot.

Then, just as they apparently reach the peak of their conquest, he then mysteriously disappears, right as the nation's enemies are at their gates howling for their blood, and then... calamity rains down from the skies, and everything is destroyed. Then he returns an indeterminate amount of time later and finds the next unsuspecting nation and the cycle repeats itself.

He outright admits this during ShB's storyline when he first appears to the Scions at the Crystarium, that he was responsible for not just Garlemald's creation but the founding of a "half-dozen other nations with imperial ambitions besides". His most recent 'imperial project' (if you could call it that), was Eulmore - he was the one responsible for Vauthry's creation as the final Lightwarden, and allowed Eulmore to control the sineaters and thus become the most powerful nation on Norvrandt (although given by that point the only other remaining nation with a functioning government was the Crystarium, it was rather moot.).

Either way, the Empire hasn't steamrolled the entirety of Hydaelyn is because they were

never created to do that in the first place - their whole point was to bring about a Calamity and then be destroyed along with everything else. They were a tool in the greater Ascian plans to restore Zodiark, nothing more.

[Cilia]

Oh definately not a troll. It just seems it is on the level of a modern army in our world attacking a bunch of cave men, and losing. Basically what your saying is if the empire got its act together and worked as a team then the rest of the world would most likely be doomed.

As much of a technological advantage as the Empire has, it's still held back by most of its soldiers being unable to wield magicks. That's a not insignificant disadvantage. Other peoples may not have its technology, but they're largely able to compensate via magic-users.

If the Empire coordinated its efforts it could overwhelm nearly anyone through sheer power and speed, but there would be a point at which other nations would band together against it. A world united against the Empire could probably overcome it, and given the Eorzean Alliance (and Doma) was able to press it so hard the Empire used Black Rose in the Bad Future... I dunno. Either way, while the Eorzeans want for technology they make up for it through magic. They aren't cavemen compared to the Empire, they're just more reliant on magic than technology.