Whilst I'm generally opposed to cinematics/cutscenes (games are an interactive medium and cinematics keep them from exploring that further): There's quite a few that enhance the experience. Like first staring into that abyss going down to the Underdark... Additionally, going cinematic seems have paid off in the bet to attract a larget audience to this type of game.
That doesn't mean I'd like to be every game to go cinematic now. Quite the contrary. It boggles the mind what this game could have achieved if it DIDN't have to keep cinematics in mind. There's an awful lot of work visibly being done here. Because Larian didn't merely go cinematic. They paired that with fairly open quest structures, customizable parties/player characters and their systems driven design allowing for emergent gameplay / non-scripted things to happen, which actually is fundamentally opposed to cinemetics in a way.
Cinematics are scripted. Emergent systems aren't. So they had to take into account all of that. During the Early Access, I thus "broke" such a cinematic. There's a dungeon with a bunch of skeletons rising if you pull a lever. This is shown in a cinematic. Apparently you cannot do that anymore as the skeletons rise immediately if you try. But during EA I reloaded and picked up the corpses and threw them into a firepit nearby. This worked... and the skeletons died upon pulling the lever. Except for the cinematic beforehand, being scripted, showing the skeletons rising in their usual place.
A more recent example of how much work went into this I only noticed upon a reload likewise: Recently, I approached a character who prior had given me a task. Basically, he knew me from a copule hours prior meeting him in another place. I approached him and he asked me about that task. Then I reloaded, transformed my character's appearance via the disguise self spell. I approached that character likewise, and the cinematic (plus VO) acknowledged that my character had transformed. Dude plain didn't recognize me anymore and treated me as we had first met. That's crazy amounts of extra work. You may not even have that spell, let alone use it here for anything. And it's still in the game. There's lots of stuff like that.
Very few, if any studios have the kind of budget to do that, and if they do, they go for far more linear experiences, oft on purpose. However, if you go for a more linear and scripted structure, less improvisation and moment to moment decision making is allowed to impact things... be it during a quest or else.
tldr; nicely done, but extravagant for sure. 
