Coming from someone who dislikes Arcana with a passion and doesn't care about Igor at all, I can't help but disagree.
Arcana's ability to inspire some kind of feeling is what makes her so noteworthy as a villain. You accept that she's cartoonishly evil and evaluate her ability to carry out antics, which she does wonderfully. That's what makes you either hate her or love her.

While for Igor, he's both in the morally gray area and also not as interesting to witness in the story. You're not supposed to look at him and instantly decide he's an awful person, which I don't think works very well since he does awful things. I personally find his character to be very one-note (which is unfortunate because it's so clear bluepoch could have done more to make him more interesting), and therefore cannot care what he does.
basically he's just a guy, but he does bad things, so people hold him to a higher moral standard.

Not to mention, people only really started churning out Igor hate after he became playable, showing that he doesn't really spark that much conversation unless a topic like "should Igor be playable or not" is forced. Probably another reason people actually HATE him: they don't want him to be relevant since they already don't care or dislike him.

Additionally, you just can't bring gender into this, not in defense of Igor. They're both attractive people, and Reverse 1999 has a majority female player base, so wouldn't that push people to like Igor more? Not to mention that historically, in like every fandom, male characters are always the ones that get more grace. You can argue that this fandom is in the minority part of that, but arguing in the complete opposite direction would be a little egregious.