Slavery never came to an end, it was simply modified in such a way that the masses could be duped into not even seeing it as slavery at all but instead seeing it as "necessary for the good of society". This is the indoctrination of the religion known as 'Statism' AKA - the belief in government and authority. If you honestly believe that you are free and that slavery came to an end, you are under the statist form of mind control put out there by the ruling class and they have you exactly where they want you.
For them, the best, effective and ideal slave is one that not only believes that they are free but will deny outright the claim that they are enslaved. Even worst they will defend their own enslavement, and make excuses for it and even vilify anyone who tries to speak out or fight against it.