I don’t know about that. She’s a bigot who is desperate to hide that she’s the very thing she hates (a half-blood with a Muggle parent, a squib brother and a father she considers to be an underachiever). She’s probably got a lot of internalized issues going on. That IMO gives her some depth.

Sometimes people are willing to throw others like them under the bus if it means personal success and being patted on the back by bigots. Sometimes people in marginalized groups (or with family members in marginalized groups) end up just as bad and sometimes even worse than your average privileged clueless bigot. It happens. Not everyone who is awful or bigoted has some sad tale of abuse or bullying or tragedy behind them. Sometimes people are just like that.

OP, do you even know why so many people united in their hatred of Umbridge, so much so that she is the most universally-reviled character, even more than Voldemort himself?

It’s because we all have been subjected to a Dolores Jane Umbridge. We all have had one of those in our lives. Because the type of evil Umbridge is? It’s real. The chances of having your parents murdered by an evil like Voldemort? Extremely slim. But the chances of having a teacher or authority figure use their position of power to traumatize you because you have opinions they don’t like? The chances of having an authority figure who punishes you for telling the truth about traumas you have suffered? The chances of having an authority figure who uses their racist and bigoted rhetoric to keep you in line, and you know you can’t go to anyone else because if it’s your word against theirs well, you’re just the kid and who would trust the kid over their teacher, right? Everyone has a story they can tell, because Umbridge’s brand of evil is very, very real.

She didn’t need some sort of backstory to ‘flesh her out’, she didn’t need ‘humanity’, because she was already real to so many people who read those books that a lot of us were right there with Harry when he wasn’t sure who he wanted to ‘win’ more, Snape or Umbridge, because they were both so fucking awful. And, like lupinatic said, sometimes people are just fucking awful human beings. And to be honest, I am not interested in hearing my fifth grade teacher’s sob story. I’m not interested in knowing why she thought it was ok to watch the entire fucking class bully me and physically assault me (not just outside class but in the classroom under her supervision) to the point where I was scared to wear dangly earrings or necklaces to school, and then call me a liar to my face when I tried to tell her about it because I was so fucking desperate I was willing to be a ‘tattle tale’ just to make it stop. I’m not interested in hearing why she found her fucking romance novels more important than teaching us. And I wasn’t interested in any of that with Umbridge, either.

Frankly, there comes a time when it’s insulting to give a character a sob story and make it seem like we’re supposed to sympathize with them after all the shit they pulled. With Snape it came very very close to crossing that line, although the backstory itself was important and I could get past it for the sake of the story. But with Umbridge? It would’ve been absolutely horrible.