Gatsby isn't supposed to be bad. He's supposed to be tragic.

The bad guys in Gatsby are Tom Buchanan and, to a lesser extent, Daisy. One might make a case that Nick is not a good person, but he's telling the story as a salve for his guilt. He's mostly just a hypocrite who doesn't want to admit he's the same kind of wealth that grinds non-wealthy people up for pleasure.

But Gatsby is a man who became obsessed with a woman and did everything he could to win her heart, including fraud. Yes, that's not good behavior, but he's not meant to be taken as a bad guy so much as someone who made some mistakes because of higher emotions.

Tom OTOH is just toxic masculinity. Fucks other women, can't stand any other guy getting attention, doesn't give a crap about people who die, etc.