What's the point with that quite lackluster story in Endwalker?

[Rilifane]

I'm still confused by the idea that the Garleans were ever anything more than "generic evil empire". That's pretty much been their entire schtick since day one.

It's cool if that's what some players like, but Garlemald was trying to do the same thing in Stormblood that they were doing in 1.0: build big machines and use them to conquer the world.

They were definitely presented to us as such at first because it fit the narrative of "we good, Garlemald bad!".
I would've preferred if more lore surrounding Garlemald had been presented to us via ingame resources sooner though.

I personally liked the lore surrounding Garlemald and the nuances of its inhabitants. It was race almost pushed to extinction by being biologically inferior to the other Eorzean races as they alone were unable to manipulate Aether - something the whole planet is overflowing with. That's a pretty insane weakness if you think about it and makes a lot of their way of thinking and acting completely understandable. The biggest source of power, readily available everywhere, was out of their reach and everyone and their aether-manipulating cats walked all over them.
They found a means to survive in a harsh, cold part of the land through technological means and discipline. The strict order and discipline wasn't all the Ascians' doing, it was necessary for survival.
And then you got more and more glimpses of the internal differences like Gaius not agreeing with Project Metetor or Black Rose or Regula not agreeing with trapping primals and thought it a too unstable and unpredictable means especially after the disaster with Bahamuth and fighting honorably or Maxima being a diplomatic person that tries to think of the civilians and wants to minimize any form of unnecessary destruction to both sides of the war. On other side of the scale you have characters like Asahi who sold out his own sister.
Then there were the conscripts that found a new purpose in Garlemald's legions and those who were only biding their time until they saw a chance to desert. If they had introduced more characters like Regula, Maxima or the Gaius we later come to know a bit sooner I think many would think different about Garlemald - because the nuance was there the whole time, they just purposely didn't tell a lot of it until last second and via side quests because it wouldn't fit the "Empire evil hehe" narrative.