One of the only freed house elves we hear about literally drinks herself to death because she can't 'handle' freedom, which was a defense of slavery back in the day.

Also, even more eerily, Joanne has tried to retcon Hermione as black. When you then read her as the only character to try and free the house elves, something everyone makes fun of her for, it becomes EXTREMELY unsettling. Even if she weren't black, it's upsetting, and not because we're meant to see how problematic the Wizarding World is. May I remind you, Harry also thinks she's being crazy for trying to free them, and he's just as much of an outsider as she is. When all characters from all walks of life in a work believe the same thing like this, it feels very much like it's the author who believes it and is putting it into the work.