I posted this on reddit as well if you want to join the discussion there.
The Core of the Game
Despite this game being an open-world action RPG with all the trappings that that genre implies, this game is at it's core about relationships. Specifically about Geralt and his relationships to the people around him, his "family". This is easily one of the most personal games out there, despite it being full of politics, war, and monster slaying. We, as Geralt, get to be involved in other people's stories for a time and possibly shape how they end. It's so well done that it becomes frustrating later in the game when these relationships fade into the background. If this were a movie or a novel it would make sense as the plot must move ever forward. This isn't like a movie or a novel in that respect though. The plot can be paused so that we can explore and take in the world. It can be experienced in different ways in different orders or multiple paths. So when the relationships that Geralt, and the player, have taken all this time to build get stuck despite the rapidly changing world around them it feels like there's a hole that needs filling. I believe that these issues should be a major focus for CDPR before moving on to their next game.
Ciri
Thankfully, the central most relationship (Geralt and Ciri's) is also the most explored. That said, it isn't without some oddities: The choices that govern Ciri's fate feel a little trivial. They seem like small moments and decisions in between much larger moments and decisions. I get what the devs are going for here and I agree with them to an extent. I just think there needs to be more decisions that matter. Right now Ciri's fate rests on five decisions Geralt must make in the game:
1. You have to have a snowball fight with Ciri.
2. You have to refuse payment from Emhyr
3. You have to let Ciri talk to the Lodge on her own.
4. You have to let Ciri ransack Avallac'h's laboratory
5. You have to help Ciri bury Skjall.
The choices you make lead to one of three endings:
1. Ciri is (possibly) dead, Geralt then kills himself by monster.
2. Ciri follows in her biological father's footsteps and becomes the Empress of Nilfgaard.
3. Ciri follows her adoptive father's (Geralt's) footsteps and becomes a Witcheress.
The only one I find a little strange is the decision to destroy Avallac'h's lab counting as a good decision. On the one hand I understand that the point of these decisions is to let Ciri be Ciri. On the other hand it seems like a small, petty, decision especially considering the effect it can have on the ending. It would be nice if, for example, helping the elves (during the "Payback" quest) steal the horses also counted positively to her fate. In fact, I believe most of Geralt's interactions with Ciri should count in one way or another. For instance, it would be nice if Geralt could lose the rock-paper-scissors game (or choose to let her go) and then Ciri could fight Imlerith herself (counting as another +1).
Another thing I want to bring up is the reason Geralt's decisions matter so much to Ciri. For someone as strong-willed as Ciri is it seems strange that what Geralt says to her would decide whether she dies or not. Having more instances where what he says counts helps but I believe it would be much better for her to feel like she is alone right at the end. The strongest way this could be done is if Avallac'h betrays her for his own ends. This means that the only people left for her to trust right at the end is Geralt. This makes what Geralt says to her more important than ever in those final moments.
Romance
I've seen a lot of people mention that the romantic content is weirdly paced and doesn't have a proper pay-off in the last part of the game. These are some fantastically written characters and it really feels like one of the biggest choices we can make in the game. Unfortunately, the game has little reaction to this choice. If you choose Triss, she becomes little more than a background extra after the main Novigrad segment. A lot of the conflict that would be a natural consequence to such a choice is ignored. While, Yennefer is better represented in the last half of the game she is barely present for the first half. Players start off with an unfair opinion of her because she seems quite cold towards Geralt at the beginning. The scenes in Vizima hint at a lot of the different colors of their relationship but we just don't have enough time to get used to her character.
There are a few ways to improve these issues. In Novigrad, Triss and Geralt could call Yen with a megascope for a status update. She could show a little bit of her softer side, even show a hint that she and Triss are/were friends. Some of the starting quests in Skellige could have their level requirements lowered. Later, a scene could play out where Yen and Triss confront each other. It even feels like the part in Kaer Morhen when Yennefer tosses the bed out the window is a good starting point for a confrontation:
1. Yen throws out the bed.
2. When we arrive Vesimir mentions it.
3. We go to the bed in the courtyard and Triss is standing next to it. Cue conversation.
4. We confront Yen and she teleports you to the lake outside.
5. You return and Triss is there this time and the argument starts.
Pieces of the argument could differ depending on who you romanced but no matter who you romanced I feel like this kind of confrontation could still happen.
It would be nice to see Ciri react to Geralt's choice and bring it up at some point. Triss is like a sister to her and (if you romance Triss) Geralt and Yen become like an ex-husband/wife, that has to affect her in some way. I also would like to see some scenes between characters that don't really share scenes. I would love to see Yen and Ciri have more mother/daughter time, or Yen and Triss try to reconcile their differences, or Ciri and Triss share a moment. These characters are all closely linked and we only get hints towards this in the game.
Finally, an extended epilogue (even if it's just a small scene in Dandelion's inn) would allow fans to say goodbye to many of these characters since this is probably the last time we'll see them in any major capacity. There are also questions left unanswered as to the fate of some these characters. What happens to Triss if you go with Yen or Yen if you choose Triss? What happens to Dandelion, Zoltan, or Priscilla?
Eredin and Other Antagonists
I'll be honest, I don't really know how some of the antagonists can be improved here. This is where a more extensive book knowledge might really help. I do know, though, that the antagonists are barely developed in this game. A good villain has a strong antagonistic relationship with the protagonist and the Hunt seems to have an inherent connection to Ciri, Geralt, and Yennefer that has been hinted from the two previous games and the books. Unfortunately, it's barely explored. Eredin is an imposing figure and has a lot of potential but it feels like there are motivations there that aren't strongly established. Does he want to bring his people to this world and conquer humanity? What's at stake for him if he fails? What did Geralt do while he was with the Hunt? What does Ge'els want? How does Avallac'h have such a large change of heart from the books to this game? Avallac'h briefly talks about Caranthir being his protege but we don't get any dialogue between them or anything further development of that relationship. We have very little context for these characters and if CDPR can fill out these characters and how they relate to each other it will help fix some of the issues with the plot in the third act.
We also have characters like Djikstra, who seems to have a grudging friendship building with Geralt, take a sudden left turn in the "Reasons of State" quest and betray a bunch of people close to Geralt. This is presented to the player as a choice but considering our relationship to him versus our relationship to the others we would have to let die (Roche, Thaler, and Ves) it's not a hard one. In the end it feels like a contrivance to further the plot rather than stay true to the characters or even CDPR's intentions with player choice. Other characters like Francis Bedlam and Cleaver just seem to disappear when it seemed like they would be playing a large role in the endgame.
Conclusion
I know this is a popular topic for discussion and some of you might be sick of seeing posts like this, but we see them because what we have in the game resonates with a lot of people. I love this game. I wouldn't be writing this wall of text if I didn't already believe in this game and it's developers. It is absolutely one of my favorites but it is not my all-time favorite YET.
I want to draw to people's attention to the fact that CDPR have said that they have no plans for an Enhanced Edition at the moment and I think the community needs to continue/renew calls for one. If you guys want this let CDPR know, even if, in the end, all our complaints can't be fixed. I think we would all love to see CDPR properly payoff the story they have so expertly crafted.