Exactly.
I'm gonna be honest though the "let's stop slave traders" arcs can be annoying sometimes like in "Snow White with Red Hair" and "Yona of the Dawn". It's like they copied eachother. I remember it being so prevalent in historical romance manga and they felt the same.
Maybe if the subject is taken lightly or isn't the focus it shouldn't be included at all?
Some stories show the truth, that many people are powerless to stop the evil. It's horrible but that's just how it is. You don’t see people calling for Red Light distructs to be destroyed in manga. Like when the woman is selling her body people only talk about her getting bought out of the life. The system is the problem.

It irks me a bit when people complain because of thing like slavery and ML doing villain thing or if the FL don't care much about the Slavery going in her kingdom...mind you this is Historical manhwa based on you know where period where Royalty, commoner and slaves exist? If don't want to get surprised by that kind of thing maybe just maybe avoid that genre and not complain about the author work and also make yourself a hypocrite...what Top it all was the people complaining the FL Villainess doing like you know 'Evil' thing like its there on the title so why act like some blind