You and I disagree on this and I'm 100% with Larian and Pathfinder on this issue. WotC tried to eliminate alignment in 4th ed and it was one of the (many) reasons fans rejected it in favor of Pathfinder . . .
What do you mean you're with Larian? Have you found any materials from Larian confirming that Minthara has an "evil" alignment? I'm not aware of any.
As others have pointed out before, BG3 has lots of characters playing against type. We meet a "good" githyanki and even a friendly mindflayer.
People just like alignment. Witness the thousands of alignment grid memes.
I disagree. People like it for the same reason people like horoscopes. It's just about putting people into prescriptive boxes. We might as well be trying to work out whether Minthara is a Sagittarius. Whether or not it's helpful is a separate matter.Here
Zaeed Massani -- a bounty hunter who will literally kill anyone (good or bad) for money -- is classified as "True Neutral" basically just because he's not eating babies for fun. For the record, a bounty hunter who's happy to kill good guys or bad guys as long as he gets a paycheck would be better described as evil.
But what do you think in regards to the "lawful" thing? From memory Zaeed has a strict code of honour that he follows, so I'd classify that as "lawful". But on the other hand, he has no regard for the laws of governments and murder is against the law. So is he lawful or chaotic?
In contrast, the spectres are special because they are given the privilege by law to ignore the laws everyone else needs to follow. Does that make them lawful or chaotic?
(There is no correct answer to these questions.)