1. Linearity. Witcher 1 was already pretty linear, but Witcher 2 takes it to an entirely different level. You aren't allowed any detours, or to develop the story through initiative and discovery. Instead you are shit through the plot, beginning to end.
Agreed. Even though the general structure of TW1 was very straightforward, the quests themselves where often quite open, seemingly spreading into a dozen different directions and even mixing into other quests before eventually reaching their conclusion. In TW2 the main quest is much more straightforward, as in the first act you basically only get a couple of objectives that you can do in any order while everything else is set on rails, and the openness in the second act comes mostly from collecting a ton of different items, which is alright but not nearly as interesting as, say, Act 2 of TW1. The side quests don't really tie into the main narrative in any way either, unlike in the first game where you got to meet Kalkstein, Abigail and a bunch of other characters by doing witcher work for them before said characters even became important to the story.
2. This sort of ties into Point 1, but you don't feel like an actual witcher. The whole game is about Machiavellian political intrigue, without actually involving any real Witcher duties. Witcher 1 had the Salamandra/Grand Master as a driving force, but Act 1 focused on freeing a village from a hellhound, whereas Act 3 (?) involved lifting a curse. Witcher 2 has Geralt relegated to some sort of political pawn, where he occasionally tags along because more powerful individuals are like "Oh, you have a silver sword? You might as well tag along in case we run into monsters, lol"
Well, the vast majority of the second act is about lifting a curse. It's maybe a bit overkill for an ordinary witcher's job, but it fits the tone of the game very well. The monster-killing quests are also generally more interesting than in TW1, although I do miss spending the majority of my few orens on monster books. I personally didn't mind the political focus or the change in the game's overall tone and thought it was a logical follow-up to the first game's more down-to-earth approach.
3. Witcher 2 lacks personality. All the 'political intrigue' just strikes me as try-hard, and doesn't resonant with me. I can't think of any event in Witcher 2 that was memorable. Witcher 1 had quite a few memorable moments. Saving Abigail from the mob, Vincent fighting by your side after freeing him from the curse, the party at Shani's house, playing detective for 'Raymond', finding out the truth about Berengar, lifting Princess Adda's curse. Witcher 2 just felt like I was ticking off boxes and going through the motions. Oh, and look out, dragon!
I don't know about that, I think there are plenty of memorable moments. Then again, I love the politics in the game. I guess one difference is that in TW1 it felt like you had more control over your actions whereas TW2's cutscenes feel a lot less personal. In TW2 you often become just a passive observer and feel like you have little control over Geralt's actions. Many of TW1's memorable moments were pretty low-key, perhaps just a piece of dialogue somewhere where you learn something new about a character that has been around for ages, Shani's party being a good example, or a choice that had been patiently built up for a while, like having to choose between Abigail and the villagers. TW2's pace is a lot more frantic, so individual moments like that don't really stand out in the same way (especially if they're delivered in a form of a cutscene over which you have no control).
For me TW2 was an initial disappointment partly for the reasons you mentioned, but I've come to appreciate in a lot more after subsequent playthroughs. Although it loses to TW1 in many areas and is overall probably not quite as good, it does a better job in some other areas, like C&C, characters, story and writing in general, and as a result its game world is notably more cohesive. I mostly just miss the slower pacing and player initiative of TW1, along with some mechanical stuff like the alchemy and inventory systems.