I think it's kind of silly to be comparing The Witcher 2 and KoA. They're just about as far apart as you could possibly get in terms of design, world building, atmosphere, open-world vs. story-driven, grounded "believable/realistic" fantasy vs. extremely high fantasy, etc. The Witcher 2 was not going for an open-world experience, and nor should they have; it was meant to be a story-driven experience with a "less is more" approach to world design. The game didn't have massive areas to explore, but each area was very well-made and full of great writing, strong atmosphere, and memorable characters. Free exploration between these areas would not have made any sense in relation to the story, so I'm not sure why some people criticize this. Would it have made sense to be able to return to the Le Valette castle after the prologue considering the events that transpired there? Would it have been logical to be able to outright leave Flotsam when there is a sense of urgency to the events transpiring in the story at that time?
No single game can accomplish everything, and expecting a game like TW2 to have a large amount of exploration-driven gameplay or KoA to have TW2's level of story quality in an open-world game is being unrealistic, in my opinion. That's why there are different types of RPGs that offer different experiences, as there will never be such a thing as a perfect RPG that contains every possible great element contained in the different approaches to RPG design.