I'm ~25 hours in, and this really is one of the most visually inconsistent games I've ever played.
Some sections look incredible. Other areas look like they're from a low budget PS3 game. Some environment textures take a while to load in, and others are just permanently at a PS2-level state. The models for the main characters look incredible, while most of the NPC's look worse than those of GTA V. And they're repeated everywhere too, even within the same small towns. I'm not someone who usually would even notice this kind of stuff, but it's pretty blatant.
And the environments aren't particularly expansive either, so I'm not sure what happened.