I suspect they're not using techniques like procedural generation, which can pack a lot of highly detailed graphics into a tiny space. It's the difference between a vector and raster image.
You do not use realtime procedural textures in AAA games. The resolution for those needs to be quite high (2048px or 4096px) and compiling the shaders into that resolution takes ages.
They however do use procedural textures when texturing objects (Check Substance Designer), but having to compile them during playtime would make load times unacceptably high. Maybe even hours.
They however do use procedural textures when texturing objects (Check Substance Designer), but having to compile them during playtime would make load times unacceptably high. Maybe even hours.