Yes, people eventually came to recognize slavery as being immoral, but it still hasn't stopped it happening today.
What is not a pointless question is, how is it that a supposedly all-powerful omniscient being didn't appear to recognize the immorality of slavery? The bible records this being punishing people, often by having them killed, if they committed acts it considered offensive to its being, but not for being involved in slavery. Instead, this being produces the slave owners guide to good slave keeping, which can only be interpreted as condoning the practice. What do you think?
The slavery that happens today is the province of pimps and criminals, and otherwise very creepy people. It is the dregs of society, the ISIS, and the ruthless who for the most part operate in the dark. Slavery is against the law everywhere, with Saudi Arabia, from what I recall, being the last to make it illegal somewhere around 1960.
This is something that is unprecedented in human history, and likely even in human prehistory. Slave owners even up to one hundred and fifty years ago were esteemed and privileged members of their perspective societies throughout all of human history until that time.
Now I don't presume to understand the ways of God, and I don't second guess him as you do. But, we can have some inkling about is human nature. Human nature is such that Japanese military leaders in the second world war used their POWS to test the effects of frostbite by freezing their arms in place and then pouring boiling water over their frozen limbs until the flesh flayed off. Human history is filled with such examples of incredible cruelty, and I think if we are all honest with ourselves, we might know that our own imaginations are not also sometimes given over to acts of cruelty to those who we are fighting with.
This is the kind of human nature that we are dealing with. The earth from the very beginning, from the time of Cain and Abel, was polluted with the blood of the murdered and the oppressed, and this is the humanity that God chose not to wipe out in the Flood.
Now that we are in a positon to self-destruct, through birth control and abortion, and weapons of mass destruction, it is hard to say if we will make the same choice as God did, and keep the human race going.
But in the meantime, it is all about how to get from there to here, from the there of dominance and enslavement no doubt inherited from the gene pool we share with the dominace hierarchies of chimpanzees and the animal kingdom, to the here of slavery being outlawed.
Now you don't have to believe in that supposed omniscient King Monkey in the Sky if you don't wish. You can play the aha gotcha game with the Bible all you want.
It doesn't change the fact that the way we got from there to here on the issue of slavery in the nineteenth century is with people reading their Bibles, and figuring out a way.
Now the way that I see it, the Bible is not a simplistic sort of text. It is honest and it is deep, and it contains the struggles and the missteps of people from the bronze age, or earlier, and moreover preserving even earlier oral traditions into their efforts to find out where the good lies The lessons of the Bible have to give are therefore both ageless and progressive. We still struggle to find out where the good lies. Our story of our struggle with God has not been written yet.
But here is the amazing thing. People connecting with the ageless stories of the Bible were able to achieve something that is completely new in human history, and even human prehistory. They were able to create a sustainable world without slavery.
You can dismiss the supposedly omniscient God all you want, but the fact remains that you didn't end slavery. Those in Britain a scant few hundred years back did that for you, and they did it through being inspired by the hopes and dreams of Bronze Age people, and the people that even proceeded them.
Dismiss it all you want. In my books that is pretty remarkable, something to remember about the British.