The more I think about it, the clearer it becomes that the game's writing is not all that praiseworthy.
Velen really is brilliantly written, both the main storyline and the individual characters there. You have characters that feel believeable, have their likeable side as well as some major flaws, and the characterisation is miles beyond your usual "good guy with a dark past" or "asshole who means good" archetypes of morally grey characters you see in games. The storyline manages to remain consistent about its themes and has a very satisfying conclusion.
After that the quality of writing drops quite a bit. There are still some great characters in the game, the quality of dialogue remains high most of the time and some individual scenes are simply outstanding, but the storylines as a whole don't manage to explore any meaningful themes in depth, making them feel rather shallow and unsatisfying compared to Velen. Many of the characters also come off as fairly simplistic archetypes, something that CDPR have usually tried to avoid or at least twist in some way in the past. In Novigrad, especially, the game starts to drift more and more towards black and white characterisation, having clear good guys with practically no flaws at all and bad guys whose badness is constantly rubbed in your face. You get a completely paranoid religious fanatic who loves to burn people at the stake, a crime boss whose favorite pastime is nailing whores on his walls, a formerly harsh but adequate ruler that has now turned into a drooling lunatic that organizes mass murders for fun... These guys make Bernard Loredo seem like a stable and likeable if a bit misunderstood Sunday school kid in comparison. Skellige isn't much better, offering some slightly more complex political scenarios and raising some valid questions but ultimately not doing a whole lot with them, Yennefer being pretty much the only character that even warrants a discussion about whether her actions are justifiable or not.
The politics are just a huge missed opportunity. The story being more personal and less political this time is perfectly fine, but when your main conflict only really has two sides, it's just sad how simplified it all is considering how elaborate the politics of the previous game were. Everything basically comes down to one or two decisions the player gets to make, and the game makes even that a very straightforward affair, demonizing a certain individual throughout the whole game and not even allowing you to have any in-depth conversations about the pros and cons of each possible end result. Your choices regarding politics and the state of the world have little to no effect on the main quest or any other quest for that matter, being almost entirely on the background for the whole time.
The main story is functional during the first act, when it barely moves at all. When things finally start moving forward, the quality drops massively and it all becomes awfully shallow. Many aspects of it make little sense or go nowhere, and even though almost all of the individual quests are good and interesting, they don't form a coherent or satisfying whole. You go on a hunt for certain individuals that are supposedly important but don't really do anything. You embark on a search for an artifact the game just pulled out of its ass because it... does something. The only twist about the main quest is that there is no twist. The bad guys are essentially non-characters, just a bunch of evil-looking guys with deep voices that spout out a few generic taunts and that's pretty much it, which is a gigantic missed opportunity considering their backstory and the fact that they have a very good reason for doing what they do. I mean, they seem like perfect villains for the CDPR writing team, being considered evil but ultimately sharing motives that are very similar to those of humans', but instead their portrayal is as one-dimensional it gets (in before joke about all that travelling between dimensions). Oh, and of course there's a deus ex machina at the end as well, just because.
Maybe it's the lack of time, maybe the fact that the writing team was almost entirely different than it was in the previous game, but the main story is just so disappointing considering the quality of the first two games. I really wanted to love it, but it's just not very good. The general level of writing is still high, the side stories are mostly excellent, the game has a ton of great characters and most of the dialogue flows so naturally that it quite simply puts almost every other game to shame, but all things considered, I'm not sure if it's even the best-written Witcher game as a whole.
