Why is he so unpopular with women? you'd think they'd love a brooding noble type

His competition is a sexy vampire, sexy smart nerd and a sexy buff good guy druid. The game was rigged from the start

this isn't true.
People just hate him because he's this goody two shoes to the point that it's boring. I know this one girl who like him and even she was like "I know I know he's boring but I still like him!!!"
Both men and women like Astarion because he's such a horny and fun character.
People like Halsin because he's a bisexual bear who takes good care of people

Is he popular with men?

not at all.

most of the followers in BG3 are interesting. Shadowheart gets a boost from being tied directly to some of the story archs in act 2 and Lae'zel is a githyanki with the most natural character development. Gale is the wizard with a cat.
No reason to use any of the other story characters they're all tropes and shit.
Astarion is every bad Romantasy trope, Karlach is le tough girl, wyll is the rich kid.

aren't interesting

not sure how i missed that but I've been day drinking.

White women don't actually like niggers. That's jewish propaganda rotting your brain.

all these people coping that he's unpopular because he's too good or too boring

It's because he's an ugly nigger. That's it.
Replace him with a 7 feet tall paladin that looks like Arthas without changing anything else and let's see how he ranks.

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Whether it's The Sims, or Baldur's Gate III, female streamers and players across all platforms showcase an aversion towards black characters to a hilarious degree honestly.
I guess Diddy, Cosby, Kanye, and Eddie "My Wife Fucks My Son's Friends" Murphy have ruined all their impressions.

You aren't wrong for the fact that 3 of them are tropes but they're fun to hang out with so fuck you

Not gay enough, same reason why the other guy on the Team is not that popular with the women "gamers".