Don’t even bother making a new game unless it supports ray-traced light speculating through the anal-fog discharged from the main character’s arse. Every single pebble too within a 50 mile radius must be able to reflect the dripping, wolf-ey arse sweat drops too at all times using some buzzword engine tech or no one will buy the game

Doom had some pretty dark levels especially in a lot of the additional episodes and I personally think they were amazing. Half-Life 1 and 2 are similar and they're both legendary games. Personally I would put the point where gaming started to go downhill at 2011 (with the release of skyrim).

Brown and dark was the Xbox 360 era. We're in a post Fortnite, Rocket League, Minecart world now. The trend now is tons of color but in a way that I'm starting to get a little tired of everything looking like the same purple.

Lots of good, new stuff in the boomer shooters. If you want to try something like Duke 3D, check out Ion Fury, which was made in a fork of the original Build engine. Seleco and Hedon for modern GZDoom stuff.

Corn Kidz 64 has the best graphics of any game of the last 20 years. I will fight and die on this hill.

I don't think there's anything stopping modern games from having the same vibes, and being creative with graphics. I'd say one example of a modern game with high res graphics, realistic water, and even ray tracing, which still looks very unique and distinct is Paradise Killer. Another one that also looks quite modern in some ways while still being very distinct in its own way, is Heaven's Vault. It's a choice made by AAA studios because photorealistic visuals tend to attract more eyes and sell better, even if people get bored of the game quite quickly.

And the thing is, AC Unity - which came out in 2014 - still looks better than the majority of AAA games I see nowadays, and despite the large crowds which are a bit CPU demanding it still has much lower requirements than those games that look worse.

EDIT: And if you just want games that actually look retro and old school, there are some from indie devs doing that; examples include: Dread Delusion, The Case of the Golden Idol, Death Trash, Felvidek, Return of the Obra Dinn.