I’ve made my opinion clear on the Bone, Stone, & Obsidian Podcast, see eps 14,15,16 about 5e Dark Sun.
The Dawnlands Kickstarter is exactly what would happen if WotC didn’t consider the history of the setting against modern values.
And to be clear “modern values” doesn’t mean no slavery. As many have pointed out slavery is a staple of fantasy and post-apocalyptic fiction. Where Dawnlands failed is that they leaned into the brutality while failing to illustrate slavery’s negative aspects by choosing words and phrases that put people off.
The original TSR Code of Conduct from the 90’s states, “Slavery is not to be depicted in a favoriable light; it should only be represented as a cruel and inhuman institution to be abolished.” While that is a fine statement I don’t think it’s detailed enough. We not only have to consider how the element is show in the game world, but how it affects the players as well. Slavery and its effects on the lives of people are a reality. As a result game products should not put players in a position to suffer slavery without their consent. This is the consent of the player, not the character. Some people might balk and say do you require the consent of a player to kill the character? The answer is usually no and the reason is because the rules for combat are clear and character death is possible.
A lot of this also blurs into the lines of controlling another players character (whether Player or DM) and mind control. I think mind control is a staple of fantasy and sci-fi so it often gets a pass, but having your character do something that’s abhorrent to their can be psychologically damaging to the player and should be considered, same with slavery. Now, again, this is not to say that it shouldn’t happen in your game, it should just be consented to by the players. And as many have said, this can all be done with a good session 0 or email discussion with your fellow players so no one is taken of guard.
I’m pretty confident that no modern published D&D adventure would mind control a PC and have them do unspeakable acts, neither should one force characters into the physical and psychological torture that is slavery.
So, to summarize, it’s all about talking with your players and getting consent, a simple understanding of what’s possible and probably in a game. If everyone is cool with it, then have fun.