modern slavery is just an extension of every civilization of the past

Every ancient civilization was based on slavery. There had to be someone to do the manual labor that built the empire. Monuments had to be built and granaries had to be filled. The royals, clergy, and bureaucrats were the educated elite that prospered from the toils of slavery.

Slavery has served as the foundations of civilizations even into modern times. The U.S. was based on slavery, which without, would not be the wealthy nation it turned into. Slavery is free money to get you started in your empire. It gets you over that initial hurdle of starting an empire with little money. If you need money to start an empire but you need an empire in order to make that large a sum of money then your answer is to use slaves.

Has slavery really ended though?

Slavery most likely began from the enslavement of defeated foes in war. You took the families and brought them back to your home and made them your slaves.

Modern corporations vanquished small companies and left the employees out in the cold to rot. They now have to come groveling to the corporations for employment on the terms that the corporation sets.

If you are working for the benefit of others instead of you and your family then are you not a slave? If you are not sure if you are working more for someone else's benefit than your own then ask yourself this: Who gets richer from your labor? Do you or does your boss who is already rich? Is it the usual case of the rich getting richer? Someone is benefiting a lot more from your labor than you or your family. Has slavery really ended?