That's only because as time goes on, the closer games get to looking like real life, the evolution of graphics quality is seen in smaller increments. That's just the way it is.
Yeah, I get what you're saying. But 2013 was like a switch was flipped. There wasn't a smooth transition from 2012 to 2013. It was like 2012 games look like crap today, but 2013 games all of the sudden became drastically better to where they still look good. To be clear, I'm not saying all 2013 games were like that; just that's when it started. But I think I've figured out that it's because that's the year the PS4 and the next generation of consoles came out.
Getting off topic, but I'm guessing polygon counts. Looking at my Skyrim pictures from around 2012, it's on the cusp of looking modern. Characters are pretty close to having "enough" polygons. The landscape, not so much.
Tessellation was also a huge deal. The ground started looking like ground instead of flat polygons with a texture painted on them. I remember The Secret World had that, and it released in 2012. It got more popular over the next few years.
Man, I thought the exact opposite about Skyrim. I mostly played the Special Edition, which had updated graphics, though. But I thought the environment was beautiful, but the characters were the main problem, graphically. The character and facial animations were atrocious in Skyrim. It's my favorite game, but that wasn't spectacular. I'm really,
really hoping TES VI is a lot more modern looking.