I think most of us who read historical novels or watch movie and t.v. presentations develop an interest in history. "What was it Really Like?" we ask at history sites. We look around. We imagine. We ask questions, no matter how ill-formed and ill-informed. We read history books. And we critique the books, the movies, the history interpretations with the information we accumulated.
I think most of us are aware from school slavery was part of life in ancient societies, the Middle Ages, and the American South. I was surprised to read how long it lasted in the North and in Canada. And we have always been told until lately that a woman's life purpose was husband- , home- and child- care. What we're used to, we take for granted and don't question until we are confronted by an incident or person who makes us ask ourselves "Why?".
If the racial / gender issues are incidentals to add color, ask yourself if your characters think they are issues or if they don't. For example, Huck Finn took for granted that Jim was stupid because he was Black, and that it is right and normal for black people to be enslaved. Huck and Tom takes them so for granted that Jim's slave status is not an issue in the previous book "The Adventures of Tom Sawyer". Jim is Miz Watson's slave like Tom is Aunt Polly's scamp of a nephew and Sid is Polly's sanctimonious nephew. Not an issue. It does figure a lot when Huck is confronted by Jim's request to help him escape to the North in "The Adventures of Huckleberry Finn". It was not "an issue" in Gone With the Wind for Scarlett's mother to do all the work of managing Tara while Scarlett's father struts about the neighbourhood taking the praise for her efforts. Women did the child rearing and nursing because they always had done it, and they ran the farm too, like Abigail Adams did when her husband John was doing his important work in the Continental Congress.
As the others here have said, just because it was the "norm" to most people, it does not have to be so to your characters. Women would not have the vote if other women did not constantly insist they should have it for over a century. Those women made a non-issue taken for granted into an issue that they would not give up. Same with the abolition of slavery. Jane Austen did not make slavery an issue in any of her novels, but she had her character Jane Fairfax in Emma compare being a governess to slavery and showed how unfeeling an clueless Mrs. Elton was when she piped up, "My brother-in-law, Mr. Suckling, was always a friend to the Abolition." No one in the novel asked if Bristol based Mr. Suckling's wealth may have came from the slave-trade. I suppose it would be impolite to inquire. Mrs. Elton was admitting the slave-trade was an issue, but not an issue she was concerned about, though she was pushing Jane into accepting the governess fetters Jane did not want.