Having an option for some brighter colors is not a bad thing. Personally, I use my GForce Experience settings to brighten up the environment a bit. There is absolutely nothing wrong with wanting something like this.
D4 colors are amazing, it is reminding my Bubba from Forrest Gump!
You can enjoy red blood, red enemies, red skins, red skills (but I think I saw once or twice also blue), red floors, red walls, red air, red sky, red deadeffecte, red explosions, red…
I don’t think anyone here is saying D3 colors (except the OP). Just the option to brighten it up a bit…increase the definition so that it’s easier to see what’s trying to kill you!
If you have an nvidia card you can use filters to change the colors and vibrance along with other things. I think AMD cards use something else do do this. The graphics cards these days let you enhance the game nearly any way you want.
I keep my monitors at a very muted contrast for every day use but I want my games to be vibrant so i use filters to do this. They dont affect my every day use and are only applied when the chosen app is running.