@IrregularPerson You can spot 3d by looking for impossibly perfect lines. Completely even thickness, perfectly straight, and so on. They're also using stock photos processed in photoshop.
For example... in the "Here we Are" frame at the beginning when MC climbs out of the wagon, the wagon is a 3d model and that model is low polygonal. Tree branches are a stock photo processed in photoshop. Entire city in the next frame is a 3d model (looks like sketchup, but could be something else), and you also can spot absolutely awful textures on mountains.
In the frame titled "Grandeur", the building is a 3d model, branches are stock photo, and only crowd is hand-drawn.
When MC walks out of the gate
. The gate is 3D model, the trees near it are stock photo processed via photoshop filter. And MC is handdrawn. It is unclear if the bush with butterfly is handdrawn or not, the leaves on the bush looks like they were processed by a filter again.
------
It is incredibly common. This particular work handles 3d background fairly well, although they can still be spotted easily. For an example of worse 3d backgrounds, you could try checking "I was Trash", Chapter 6 will have some obvious examples.