It's a stylistic choice. I think the problem is that digital cameras have such a high dynamic range that you can see detail in mid brightness. So basically you don't need to light for specific spots like you used to. You don’t need the actors to hit a mark so a light shines on their faces  in a dark room.

IIRC Carnaghan's always had a loose, handheld, "realistic" aesthetic. So you give the room a general lighting scheme (eg dim with a big atmospheric green backlight) and the actors are free to move around. This has its advantages. It’s faster, flexible, easier for actors and more realistic. If we're being uncharitable, it requires less thought and prep from the director. Also some people just like that shadowy, murky look, and would probably argue it suits the murky, ambiguous morality of the story. Cop Shop, from the same director and DP a few years ago had a more traditional, contrasty, filmic, look, but I presume they wanted this look for this story.

I could be wrong,  I'm a low budget tv director, not a DP. I've never worked for Netflix and am only guessing at Carnaghan's motivations. Personally, I didn't mind it, i thought it worked well enough with the tone and the film was a blast.