Slavery-lite strikes me as a very unfortunate neologism.

I think you are putting too much emphasis on the formal status of wives a century ago, and not enough on actual social mores, but regardless of whether that is so, it is not much of an argument for what is right.

I am so confident that a robust case against slavery, that is also applicable to this situation, has already been made, that I will take my chances that someone calls "citation needed" on me.