The reason why Crowley has a better sense of wrong and right than Aziraphale (and all of angels and demons) is because he ate the fruit?
Hear me out
You know how despite being a demon Crowley has a much better moral compass than Aziraphale? I mean it’s no secret, it’s very visible e.g. during the Edinburgh minisode, the Ark scene and ofc the Apocalypse itself. He KNOWS what is the right thing to do or at least what definitely isn’t.
Aziraphale on the other hand is very much confused and mostly believes what he’s told to be the right thing. Of course that changes over time (I’m not gonna lie when I say mainly due to Crowley’s influence) but even after thousands of years he’s still much more confused than the demon. He doesn’t seem to have that sort of innate moral compass.
But the thing is, none of the angels (or demons) do, which may lead you to think that it’s an institutional problem. Which it partially is because the angels just weren’t designed to have that sort of knowledge. And neither were humans (canon Bible fact!) Do you see where I’m going?
Humans gained this „skill” through eating the forbidden fruit from the tree of knowing good and evil (or whatever it’s called). It’s very probable, to the levels where I would say almost certain, that Crowley also tasted said fruit and as a result he is the only one between angels and demons to know the difference between good and evil.