Slavery did not become popular in the 17th century. It had been popular well over a thousand years earlier and remained so.
Thank you for backing the game, I sincerely appreciate it. However your research into the subject of slavery is very incomplete. For example, institutional slavery was an old concept in the pre-Colombian civilizations in the Americas, two thousand years ago. You seem to be referring to European slavery, especially of Africans.
Please bear in mind that serfdom replaced the very popular slave institution in the Middle Ages. Also, during the Crusades, slaves in the hundreds of thousands were taken, if the slaves taken by both sides are counted. Also, the very famous St. Patrick was sold, as a boy, in the slave market in Dublin, Ireland. That was the 5th century. It was a thriving slave trade in Ireland, long before Patrick was born.
Slavery and Christianity are buzzword controversies today. My own opinion is that we do not need to fan the flames of those subjects in KC:D, both from an historical standpoint, and from a “best not to get into that” standpoint.
I feel that Warhorse will treat gender and race roles as facts of the world in the game, not as dialogues. In other words, the Church was an established fact, as was the roles women played, which are, happily, not as limited as you suggest. The game will reflect that, I believe.