See we're still just on opinions though. I'd say the progress N64 made from launch to the likes of Conker dwarfs the difference between Shadowfall and any later PS4 game.
The whole subject is opinion based, you were trying to make into a fact based argument. Gains come mostly from developers finding new ways for rendering technics, and learning how to use the hardware as efficiently as possible. It really doesn't matter if PS4/xb1 are standardized mature tech because developers weren't trying to find new rendering technics, or learn how to use that hardware as efficiently as possible before PS4/XB1 came out., The main focus was still ancient 360/ps3 till current gen came out.
Already covered this; learning to use PS4/Xbone efficiently was, by intentional design on MS/Sony's part, easier than PS3/360, hence less room for improvement over time.
Look, you can rail against the realities of development as long as you like, but there's a better option; because graphics are a matter of subjective perception, you're still allowed to think that something looks better to you no matter what the facts say. For example, even though the raw facts say PS4's power leap over PS3 is quite large, I still personally feel it was a little underwhelming, and that's okay. We all have cases where our perceptions don't align with the raw numbers. Just be satisfied with your own opinion and don't take it as an affront when the objective side is brought up.
If it seemed like I was attacking you, I should clarify that was not my intent; you seem to have taken this personally and there's really no need for that as I bear you no ill will.