Tries and fails. It never goes anywhere, and she’s mocked as a well-meaning fool for trying in the first place because “welp most elves just enjoy being slaves what can you do shrug emoji”. Jkr sets up something with Hermione and the elves and then doesn’t follow through with it in any meaningful way (and I don’t count commentary from her outside the books as following through) so it’s left to just sit there uncritically as “slavery is a thing in this universe and is seen as completely normal by most characters, and only one person ever tries to do anything about it and she’s depicted as a cringey radical in the process”. Jkr doesn’t even show the beginnings of societal change like more elves coming to Dobby’s side of things once they see it’s an option and that Dobby’s is happy that way, or other house elves being motivated to think differently about their situation and starting to unlearn their generations of indoctrination. We don’t even see a glimpse of Winky starting to recover instead the last we see of her is as a depressed alcoholic whose life was ruined by her being freed from slavery. Jkr depicts it as “yeah slavery is bad but you can’t change the way the world works so might as well not even try.” the house elves’ servitude is treated as something so fundamentally tied to their species that it seems to be biological and thus humans taking advantage of that is to some degree the natural way of things which, I shouldn’t have to explain what the problem with that sort of depiction is. Maybe that wasn’t what she intended, maybe she just added slavery because it’s a common world building trope, but if that’s the case she did so without considering the implications or how it would come across in the end product or the messages it would send.

Hermione tries to raise awareness about elf mistreatment.

For maybe two dozen paragraphs in one book, and then she gives up because literally no other wizard will support her.

Its just so funny that there’s a scene in Book 5 where Voldemort blows up a statue dedicated to Wizard Supremacy and you’re honestly not sure who the bad guy is anymore.

Then she gets to meet the slave race they keep in the basement and said slaves explain that their enslavement is a fundamental part of magic society and the only reason Dobby in particular had to be freed was because his owners were a bit too mean to him. The message becomes “slavery is fine as long as slaves are treated well.”. Then they drop that particular can of worms because addressing it would require societal change. It is one of few endeavours where the heroes of the story just fail to do what they want.