I don't see why it can't be open and still have good storytelling. If you're talking about side quests distracting from the main quest, I think that's more of a personal preference. If you like the main quest, you would follow through with it and do less side quests which will feel more like W2.
I for one, would rush straight to Yenn if that's a possibility in the beginning. Then I would take a break from the main story to focus on leveling and exploration. Then probably off to find Ciri or go straight to Skellige to find/play as Hjalmar. I dictate the pacing and the characters I want to interact with, instead of forced toward one of the paths..
Too much freedom makes story pacing extremely difficult, especially if you want to create a lifelike, immersive world. You cannot dictate story pacing yourself, you can only dictate what you want to do and that's actually the problem.
Take for example Dragon Age Inquisition (spoiler alert!): quite soon after the prologue you get the information that the life of the Orlesian empress is in danger and that somebody wants to kill her. In a more directed, linear narrative it would be quite clear that you should try to save her ASAP, at least if you don't have to do something even more important. But with its open world approach you can basically spend days and weeks with visiting different regions and areas and doing side stuff without caring about that main mission. But you still have to do it someday, there is no time trigger in the background and the empress get killed if you don't try to save her ASAP. There's the big discrepancy in story pacing. It's just extremely unrealistic and unimmersive to have literally every time of the world to progress in the narrative. Another level of this discrepancy is the balancing and game difficulty. For the mission to save the empress you get a short information that you should have met a certain experience level to probably have enough power and skills to got on. What's the problem with that? Well, you are somehow forced to break story pacing and go out exploring, doing other stuff, and at the same time you are also kind of forced to not doing too much of it because if you reached a level that is much higher than the recommended one the main narrative is just an easy cakewalk without any tension in combat/gameplay anymore.
Balancing is the biggest issue in open world games anymore. Devs followed different approaches to cope with that in the past but all have their weaknesses. One solution is to make your open world more an illusion than an actually free world by locating high level enemies in areas you don't want the player to explore early in the game. That way you actually create a kind of linear game because - if properly done - the player just have no chance against certain enemies. Good examples for that approach are games like Gothic 1/2 or maybe Divinity Originl Sin. A requirement for that solution is that you get significantly stronger during the game and that each new experience level is quite substantial. In DA Inquisition for example that doesn't work properly. Most of the regions in the world can be visited by mid-level characters without bigger problems (at least on normal difficulty). A benefit of that solution is that story pacing stays pretty much intact since you enjoy a quite linear experience anyway. There isn't a big issue with time critical tasks or emotional storytelling with tension here. The biggest "problem" is - like I've said before - that it's not really open world but more or less just an illusion, at least if you connect open world with "freedom" instead of just having a "seamless" world without loading times. Another solution is to make leveling enemies like in TES Oblivion That way enemies stay always challenging for the player, no matter how he progresses. But of course that leads to quite irritating situations in which you fight as a high class char who just managed to kill the main enemy of the game against some extremely powerful rats or other animals. It also doesn't solve problems with story pacing and time critical tasks.
Back to Witcher 3: if you take a look at the overall story it's pretty clear that the Wild Hunt is searching for Ciri to be able to invade the Witcher world and that Yennefer is also in danger somewhere in Nilfgaard. So the story already has a time critical premise from the very beginning. "Taking a break and doing side stuff" is imo just unrealistic and unimmersive because if Geralt really cared about his loved ones he wouldn't do so. If you want to tell an emotional story full an tension and a proper arc of suspense you just have to limit freedom how the player progresses. A strong, emotional, consistent story is always a pretty "linear", directed experience (which isn't a big surprise given the fact that books and movies are 100% linear, predefined stuff) in terms of time constraints (I don't mean the variety of choices here). Of course you can say that players who love a consistent story could just ignore all exploring and all side missions. But then there is again the problem with balancing (and CDPR already confirmed that leveling enemies are not planned). For which player type do you balance your game? For the story-only players? Then your main narrative will be far too easy for people who do exploring and side stuff. For the exploration type player who has no interest in following the main story? Then your main narrative will be far too difficult for people who only want to enjoy the story. Of course you could also try to find a middle way but that's very difficult and probably leaves even more people unsatisfied. Then you could make different experience levels so marginal that it isn't much of a difference but that way you also undermine your RPG focus pretty heavily. In that case you could just make an action adventure in the first place (sth like Assassin's Creed) without any significant player progression involved.
Imo Witcher 2 was a pretty well done combination between story pacing and direction and still a certain sense of exploration and freedom. The quite limited regions or hubs weren't completely linear but they were also small enough to never lose story focus completely. At the same time the story was properly directed in several acts with changing region hubs (you couldn't go back to Flotsam once you entered Act 3 for example). While not limiting the player compeletey in his freedom you always had a certain sense of story progression. And the pretty limited region hubs together with the predefined act structure also solved most of the balancing issues because you couldn't choose yourself where to travel in the world. Of course the devs didn't know how much side quests you did in the previous level/map but at least it was a far more manageable range of player experience and levels to handle than for example in much more "open" or less directed open world games like Skyrim or DA Inquisition.
My personal biggest hope is that Witcher 3 will be similar to Gothic 2. Significant player progression between various experience levels and restricted player freedom by clever enemy location. I know that that way open world isn't very free, it is more about the illusion of freedom but it would solve lots of my personal worries about story pacing and direction and also about balancing. That approach is basically more like the traditional "hub based" open world approach (like the Infinity engine games or Witcher 2) in which you are free to do side stuff but only in limited areas. While these areas were limited by level borders in hub based games you could still do a similar thing in a seamless open world game by this clever enemy location. You just have to make sure that the respective enemies are hard enough to really kind of put the player off (think of the Orcs in Gothic 2 for example, it was pretty impossible to fight against them until you reached a cerain level).
I just don't think that this is what most modern players today expect when they hear "open world". Instead they expect a more or less completely open Skyrim kind of open world in which you can do whatever you want for most of the time you spent in the game.
