This is one of this Topics, where people gradually get more ignorant. They are blinded and so biased towards their own opinion, that they don't see the core-aspect of this Topic. Try to claim their own Opinion as an Fact and talk down the opposite one. Meanwhile the Answer is so easy. Neither an Full, Partly or non,- Voice-Acting is supreriour and better, it's simply different and gives the Genre more Variety.
The Witcher 3 without an Voice-Acting would be as half as good as it is now; because the Game would have lost alot of Atmosphere. It's pretty important to the Game, and to dumb down the voice-acting to partly or even non-VO, because some Arguments like "Dialouges get scaled down..." , is pretty wrong, because in Case of Witcher 3 it's one of the Reason why Dialoges and such offers such an high Quality, because it gives the Characters life. Then again Witcher 3 is an completly differend kind of RPG than Divinity, because it is the more predefined RPG, which sets huge stone on Story as well cinematic Storytelling.
But Divinity: Original Sin (2) is more the classic Approach of the Game. It's an Game to be meant to be roleplayed by yourself and your Friends. To let the Players give the NPCs and Characters Life, due their own "imagination". Truth to be told - the Full Voice-Acting is one of the things in Enhanced Edition, which keeps me bordering, because it takes out a bit from what i appreciate in this Kind of Game, and that's why i'm atleast happy are about the partly voice acting for the Second Game. Even more when i know, what Larian would've to sacrifice to achieve an Full Voice-Over, it wouldn't worth it.
Now people would argue about the partly Voice-Acting. In German we would have an Phrase for that: "Nichts halbes, nichts ganzes". (Nothing Half, Nothing Full) I don't know if there is an similiar Phrase in English for that, but it kinda means, to do something halfheartly - like an Shooter-RPG where neither the Shooter nor the RPG Aspect really works. And i have kinda disagree with that. Because as example, Breath of the Wild showed how perfectly it can be done. You have in the one side, on the real important Aspects, Voice Acting, which is more cinematic and greater in the Storytelling, in the other Hand in the rest of the Game, on NPC Dialogues and such, the Game gives you the freedom of your imagination. So it's a win-win Situation for both sides. Divinity Original Sin 2 will obviously be different, due how not the important Lines are with voice-acting, but more the Backgroundtalking, but in Case of Divinity Original Sin 2 this fits as well, due it feels more alive, while you focus with your Imagination and such on the Important things. Again, different approaches, both are good due they fit their Concept.
And now on an pretty personal matter, for me such Games are important, to lay back. A lot of modern Games are so overflown with effects, with Graphics which phew-phew-lightning, and all day talking, it gets pretty stressfull and exhausting for every game. Thats why i'm happy for Games like this, where i can enjoy the silence!