Discrepancy in lore (spoilers)

[Cilia]

OK, a few things -

Garlemald's "air superiority" is typically showed through their use of super-dreadnoughts like the Agrius and Gration - but those have both been dealt with. Outside of those (impractically) massive vessels, it's reliant on smaller escort craft or personal flying machines, both of which can be (and have been) dealt with using relatively mundane means (magic and artillery fire).

The drawback of super-dreadnoughts is that they are expensive to build, maintain, and operate; case and point, after the Agrius was destroyed by Midgardsormr it took the Empire 20 years to build another airship of comparable size and firepower... and it got taken out of commission on its maiden voyage (shades of Bismarck, anyone?). As powerful as the Empire's magitek is, its main advantages lie in ease of use and speed - but once the rest of the world picked up on how to counter it, it's become much less effective.

Eorzea... yeah, as someone else pointed out to me the Alliance that fought the Empire at Cartenau, during Operation Archon, and at the Ghimlyt Dark are very different organizations that have gradually racked up experience in dealing with the Empire's weapons and tactics; further past Heavensward and Stormblood it's picked up two very powerful nations in terms of military (Ishgard and Ala Mhigo, respectively) and added their martial might to it, along with an alliance with the Domans for the push into Ghimlyt. Ishgard in particular is very well-versed in anti-air warfare, so the idea the Alliance of now (e.g. Ghimlyt Dark) couldn't stand up to the Empire is... not quite so strong. The VIIth had the Alliance dead to rights at Cartenau, but that was 5+ years and numerous battles ago.

(Yeah, forgetting the Empire's reliance on air power during Rhalgr's Beacon was pretty dumb, but it all worked out in the end, didn't it?)

That bit about how expensive it is to build, maintain, and operate dreadnoughts is why it rankles the IVth has one. I can believe they'd have one (though I find it perplexing we weren't informed of it beforehand, given we knew about the Gration well ahead of time), but just using the thing should be massively taxing and not at all something to be made into a diversion (as it's implied Gabranth knows Bozja is a lost cause and is just throwing resources there to keep them occupied while he solidifies a hold on Dalmasca). To a fighting force strapped for resources, an airship like that should be used for a last stand or just nonfunctional due to a lack of fuel...

[Jandor]

Garlemald's "air superiority" is typically showed through their use of super-dreadnoughts like the Agrius and Gration - but those have both been dealt with. Outside of those (impractically) massive vessels, it's reliant on smaller escort craft or personal flying machines, both of which can be (and have been) dealt with using relatively mundane means (magic and artillery fire).

The backbone of Imperial air power is the aurora-class airship, every Legatus has at least one and they're significantly larger than the small escort craft. I don't recall any instance of us dealing with those.

That bit about how expensive it is to build, maintain, and operate dreadnoughts is why it rankles the IVth has one. I can believe they'd have one (though I find it perplexing we weren't informed of it beforehand, given we knew about the Gration well ahead of time), but just using the thing should be massively taxing and not at all something to be made into a diversion (as it's implied Gabranth knows Bozja is a lost cause and is just throwing resources there to keep them occupied while he solidifies a hold on Dalmasca). To a fighting force strapped for resources, an airship like that should be used for a last stand or just nonfunctional due to a lack of fuel...

Seems a bit unfair to assume the Eorzeans can make massive progress in terms of anti-air weaponry, but that the Garleans have just stood still on improving their airships, especially as the IVth has been investigating ancient machina from Goug and there are rumours they've found a cache of Allagan knowledge.
Could have conducted research into using a different source of fuel, or massively increased their airships fuel efficiency, or even both. That airship fleet might be near enough free to deploy for all we know.

Yeah, I'm not really buying it either, but fair's fair.