FYI that's a direct quote from the book. I regrettably spent too much time of my childhood reading a series that ends with the protagonist thinking about ordering his unpaid servant make him a sandwich after a bloody battle.
Oh I forgot about Kreacher, I thought they meant Dobby. The whole thing is bizarre, Harry is so intent on freeing Dobby but then he's fine with every other house elf being a slave. They didn't even care about Hermione's initiative.
JK Rowling was trying to make the point that slaves should be slaves and enjoy being slaves, and the ones who want to be free are a rare exception, and anyone who wants to free all slaves is silly and cringe.
It's not the only example of extreme immorality that's presented pretty causally in the series.
I loved the books as much as anyone, but Azkaban struck me as utter barbarism even then. You're telling me that prisoners, regardless of what they were actually sentenced for, get psychologically tortured through the magical induction of deep despair until they develop a form of dementia? And this happens whether you're a murderous dark wizard or you do a bit of magical petty theft or fraud? The Ministry using Dementors for law enforcement would morally justify rebellion against it in my view, not only are they slavers they're also torturers on a scale that would make many dictatorships blush.
It's obvious that the Ministry a wicked institution, but it's also an incompetent one since the Dementors aren't even really loyal to them; they jump ship to the Death Eaters as soon as they get the chance to.
To be fair, dementors are consistently depicted as pure evil that has no place in society. The funnier thing for me is how the Ministry is a militarized law enforcement body that functions as the legislative, judicial, and executive branches of the magical society.
But there are things you can't unsee once you revisit the series as an adult, like all the harmful tropes that's casually littered throughout the series. From unpleasant people almost always being portrayed as fat and ugly to house elves who have a frightened reaction to the idea of being freed from enslavement, and cunning, greedy creatures with long, hooked noses that run the wizarding bank. If that weren't too on the nose, that bank even had a seven pointed star on the floor in the movies. Oh, and Kingsley Shacklebolt is quite an interesting name to give a fictional black person. And that's barely scratching the surface.
Azkaban was basically Abu Ghraib on steroids, and for any petty crime, as you say. I remember thinking "what kind of bleak dystopia are they living in, and why have they accepted it so wholly"?
Not to mention the whole "muggles are basically subhuman" thing.