For most it's runtime BGs were not gritty. Thay had some dark content, but overall the feel was of an adventure, with some dark and really silly moments inbetween.
Playing through D:OS2. and what I miss are stakes. No one really cares, nor is concerned about anything. While BG2 was bright and fun, dark stuff happened and had consequences. Things happen to people outside your party, but all Origin characters seem like a bunch of sociopaths.
D:OS2 doesn't shy from gore and gross, but it doesn't have narrative impact. Your companions are constatly snarky and indifferent, and so are most other NPCs.
I guess that's somewhat fair. I think DOS 2 focuses so much on locale-building that the world-building suffers quite a bit.
Take Act 2 - About 10-20 minutes walk northeast of Driftwood, it appears that the landscape has collapsed into a hellish nightmare world where healing hurts and a settlement is collapsing into arcane screaming torment. Driftwood doesn't talk about that, it's too busy talking about Driftwood.
The lack of world-building also hurts the origin stories because too many pieces are missing. The Red Prince was caught consorting with a demon, then was exiled by his own people to Fort Joy. He says that once he returns to his people, he'll become emperor again. Except we're missing "Step 2", which is the explanation for why he won't be arrested and imprisoned, and how he'll suddenly be promoted to the throne without his political enemies being able to stop him.
Queen Justinia of the Dwarves plans to
Can't she talk to the leader of the Humans in that area? Who is leading the humans? No one knows because Larian didn't think that was important... except that getting at least a vague idea of the power dynamics at play are important for understanding the decisions people are making.