The Hays Code was an outright prohibition of topics being presented, at all. There were some guidelines about how "positive" things had to be presented as wholly positive. And that included things like the American Flag. Which is jingoistic AF and not at all what is happening here.Not a huge fan of the emphasis on "but the work has to portray the bad thing as bad". Hays Code actually really bad. Things like it sort of bad in general too. I think sometimes it's okay if the book doesn't explicitly handhold you through whether things are good or bad. Like, I don't really entirely disagree with your vision, but any time you start saying things like "pass muster because it'd be presented as an outright evil to be opposed", you are giving me very strong Hays Code vibes.
There is no situation in which slavery, oppression, or eugenics is -not- evil. So I would want to present them as explicitly evil and meant to be opposed. Sure, you -could- write it without making that explicit, but you run the risk of people believing you endorse it or at least consider it to be a neutral fact of the world due to its presentation. Especially with a well known Tumblr meme:
I don't want that. So I will present it as evil.
If you wanna write about it in a way that isn't "Handholdy" or whatever, be my guest. Unlike the Hays Code this isn't going to be imposed on other projects or works. It's just how I'd want to do it to ensure its specific level of 'problematic' is low enough for WotC to publish.
Now if you wanna argue that WotC's standards for their publications are too stringent that's definitely something you could argue. But please do it in a thread dedicated to discussing WotC's standards for publication.