I think you're on to something here. The problem with procgen is hard because the various things in an environment have to interface with one another and in NMS they don't really meaningfully interface. The geography is generated, and the animals are generated, and the mineral deposits are generated, but the geography never affects the animals or the mineral deposits. You don't see, as an example, vast highland regions with animals adapted for living in the cold and huge mineral veins exposed in cliffs at high altitudes. You also don't see older mountains where the average mineral deposit would sit lower in altitude but be smaller due to erosion, with more cave systems and more critters evolved specifically for caves (colorless, blind, chemautotrophic, specializations like that). There's a range of ways the landscape can be, there's a range of ways animals can be, there's a range of ways resource distribution can be, but they don't affect one another and it makes it feel bland and same-y.