HDR isnt supposed to look vibrant.
its supposed to look more natural, which in turn makes it 'appear' more washed out if you are used to everything glowing with neon colours.
Ok, yeah I've heard that before, I wouldn't say I was used to it glowing with neon colours as you describe, but maybe its just personal preference. I personally find the (adjusted) game mode too dull. I've read somewhere that the game mode is really designed to minimise input lag which is obviously really important to MP games, but for SP experiences, maybe its worth all the post-processing extras as I don't really notice any lag when playing.
I've been playing a lot of horizon recently, and I find the internal areas (e.g caves/ruins) difficult to navigate in game mode as its too dull to distinguish pathways properly.
This isn't a criticism of the TV, which overall I find fantastic and i'm, really happy with. I'm just not sure if I've got it setup right for great SP experiences
PS4Pro too for what its worth.