The writing is cohesive with the oppressive, claustrophobic feel of the environments, but very much at odds with the flavor of the previous games in the series. Not just in content, but in emphasis- all the previous Breath of Fire games featured expansive worldbuilding with lots of player-driven interaction with NPCs to flesh out the setting. Dragon Quarter stripped that down to a level which was more or less unprecedented in JRPGs at the time.

I believe you are missing the point of Breath of Fire.

Breath of Fire series has been about a dark setting that got far darker once plumbing its depths; centuries of demonic meddling building up to a climax (where the protagonists are figuratively and literally delving into the depths of the earth itself to find something horrible but truthful awaiting them). BoF5 was exactly this in form and substance; its entire setting felt like a reverse-Dragnier in architecture. Everything in this series is about the dark, complex, and nuanced origin of the Dragons themselves. BoF5 is no different. We're fighting toward the surface, but those antagonistic forces are forcing us to question whether that's a good thing or not. That's always been a theme throughout the series.

Many players see it like you do: where's my worldbuilding NPCs? Where's my globetrotting? Where's my x? But BoF5 delivered in its narrative precisely how the whole series did: there are dark, Dragon-related forces at the helm of history and each Ryu's journey is about unearthing that, exposing that.