More than the specific story within the zone, I think a lot of disappointment is derived from the near-total destruction of the Garlean aesthetic and culture before we even really got to see it. Half the Garlemald zone is a complete pile of rubble, and the other half is just a snowy wasteland, so there's really no space outside of maybe the subway station to get any hint of their advanced magitek lifestyle and design. People wanted to see FF7 Midgar and instead we got FF6 World of Ruin. The Legions in the area are also either tempered or utterly destroyed, so instead of a situation where we need to make uneasy allies with the Garleans to go after Zenos, which would have allowed us to see the Garlean military from the other side, we ultimately end up just taking pity on some broken and hostile refugees, which is hardly something new to XIV.

And as it stands Garlemald and it's people just appear to be so obliterated that it's hard to consider any sort of story going forward with them. There might be a few Legions left out there, the clearly not-dead Gabranth and Gaius running around, but for all intents and purposes the Garleans as a faction appear to be done for - And we didn't even really get to see or involve ourselves with it's downfall, beyond the notion of a domino effect.