I don’t feel the diversity argument really works with BG3’s cast as they are currently designed or written, but maybe the writing might surprise me later. The more cynical side of me is inclined to think the current party members are the way they are not actually because of any evil/neutral alignment testing, but because they are remarkably close in personality to the DOS2 companions, just with way more to say. But it does make sense, it’s a lot easier to do something you already have extensive experience in.
And like you, I’m more of a Shadowheart person, but maybe because she’s the only party member right now who doesn’t appear to worship her personal ego. There’s a reason why the clamoring for other characters to join the party like Alfira (non-edgy good aligned tiefling) and Halsin (buff male elf druid) are far louder than anything similar I’ve ever seen from any other game.
