RetroGaming

Technology has slowed down, but there's also diminishing returns for what you can do with a game's graphics etc.

• The original Halo ran at 480p on the Xbox. 4K UHD has 27 times the number of pixels as that. The resolution increase from the NES to Halo was about 5.35 times.
• Games nowadays on PCs are often capable of running smoothly into the hundreds of frames per second, but of course for example the difference between 21 and 30 FPS is more noticeable than the one between 231 and 240 FPS. (Looking at you, OoT)
• Render distances are much larger with less obvious compromise on LoD.
• Stuff like ray-tracing is of some graphical benefit but is hugely computationally taxing, and there's nothing you can do about that. It's just more diminishing returns.
• Physics engines are much more complex.
• At some point, a limiting factor just becomes art direction and budget. You can have all the fancy techniques you want, but you still need to make detailed textures, animations, etc.
• The amount of polygons starts to hit a ceiling too where the model is basically continuous to the human eye, so adding more polys might only help very subtly.
• Color depth is basically a solved problem now too compared to going from the NES to the Xbox.

You can think of sampling audio. If I have a bit depth of 1, and I upgrade that to 16, it's going to sound a hell of a lot more like an improvement than if I were to upgrade from 48 to 64.