I feel thats due to how close in they always keep the camera punched, and constantly using a very shallow lens, like they are trying to hide how small and cheap their sets are. Every scene feels like its filmed in the same 10 x 10 studio space redressed and extended with CG. I dont blame them for not having the biggest budget, and accept it for what it is.
Yeah I think that's part of it, specially the extended with CG part.
I always expected the more magical stuff to look fake, but it's weird how sometimes they are just talking in a regular room or forest and the fakeness just stands out: The set looks like a set, the costumes like costumes.
Like here, even in the first shot of the trailer it just stands out how fake the background looks and how obviously they are lighting their faces with some LEDS or something.
Other shows like Vikings, The last Kingdom or not to mention GOT just sell the illusion better. But I understand it's probably more related to budget than anything else. I still wish Netflix released less original stuff but put more money into each project.