I think it's more just about material shaders.
Drawing a cylinder with a disc on the end and a firing-pin texture for shell casings, that's all pretty easy and basic shapes (and once you have one shell in memory, every other shell is the same as the last one... unless they did like crush or a unique stamp for the metal scorch.)
What's different now is that, besides having the latitude to go into deeper levels of depth with multiple rings and whatever that rectangle on top is, a modern game engine is being told, "This is plastic, this is copper, this is polished, this is rough metal." That shell model has the metal portions marked as being "made of copper", and rendered based on an understanding of how real copper looks in that light. Same for the plastic. Then a burn stamp is put on the plastic (which maybe the game knows about too? I'm assuming the burn and the bubbling on the plastic are placed there as basic stamps, but maybe they include some randomness of burn+bubbles in the calculations of the model?) and your mostly-simple shape pipe-shape looks like a super detailed and realistic shell casing, using a "Copper" PBR model that efficiently gets used throughout the game where that type of metal is used.
(*This is a really good and detailed shell here, but R&C Rift Apart has a photo mode, so it lets you see the models up close and fully detailed. I bet if you could zoom in with other games, there's probably some good shells and casings out there waiting to be discovered.)