You guys are missing the point.
I don't think anybody argues that voice acting does not, ever, never, nevereverever add anything to any game. The point is that in most cases, voice acting transits between meh and painful, so they don't add anything to these games. There are exceptions. Shocking, yeah. Some performances in Fallout 1 and 2, Bloodlines, etc are really good. I myself particularly like the voice of Morte in Planescape. And I'll say more: Witcher 3 has great moments and very memorable situations, even if much of Codex hates the game fervently. But again, that's not the point. Because Witcher 3 also has hours and hours of dull dialogues with generic performances that you start skipping without thinking about it.
But for every remarkable scene, you have hours and hours of dialogue with terrible performances in most games. Hell, even good games like Deus EX have dialogues with pitiful performances most of the time. Bloodlines would probably be a recurring example here when we talk about good performances, but even Bloodlines have its bad moments.
And that's because we're not talking about the dialogues in the "new" Assassin's Creed series, or the Bethesda games, or even Divinity: Original Sin 1 and 2. The performance in most games is mediocre at its best, and deplorable at its worst. And that's not something that's likely to change by the very nature of games. Possibly the best of the worlds would be games with limited voices, where you can record only the most relevant dialogues, and therefore, invest in good actors for these scenes. But nowadays, 95% of the games go to full VO, and the consequences of that are inevitable.