I think there ought to have been more nuanced approaches to the hypothetical world where the south won than "legal modern day slavery". There first would have needed to be a really good reason why they won- even though the South saw many significant victories in the ware, by the end of it the South was out of supplies and its armies literally wasting away. The North never saw such scarcity. Then after the deed was doneand two new countries were formed, abolitionists wouldn't have just rolled over - there would have been more conflicts between the new North and new South "countries" - perhaps in the form of trade war since they needed each other to begin with (The biggest export from NYC was cotton goods, and the NYC riots resulting from the draft to fight in the war were the biggest in US history ever at the time, perhaps since. If the south won, the North would have had to confront these internal idosyncrasis). And then there's the states west of Kansas that thought the whole affair was none of their business or at least were not nearly as invested in the matter of slavery. A show where all 50 states formed the way they have, and just rolled with legal slavery for the next 200 years, would involveso much research and nuance that D&D have proven beyond reasonable doubt to be incapable of.

I'm not a historian, I've only watched a documentary series about the civil war, and it's already obvious to me there's no black and white (hah) projection of how things might play out if the South won, or even how the South could possibly have won. What I am sure of is that D&D only see things in black and white, write things and black and white, and would have made a terrible show. Everything they ever make will be terrible.