It seemed to me like it was virtue-signalling and pandering to an audience to increase viewership or profit.

Until people stop seeing minorities as different, then these kind of labels are going to get applied just because they exist. If a cast of non-minorities doesn't raise an eyebrow, then a cast of minorities shouldn't either. Base such labels on the way the characters are written, not because they exist. Stopping bigotry requires not caring about sex, gender, or sexual orientation.

I didn’t really realize at the time how prevalent and dangerous bigotry still was in the U.S

Bigotry is a worldwide issue, not just in the US. The problem is often implicit discrimination, where someone is subconsciously influenced by bigotry and isn't aware they're doing it. It never gets resolved because people get defensive when it's pointed out to them. Stopping it requires prioritizing doing the right thing over being right.