If one wants to move what seems far afield from racism. Slavery and racism are not empirical equivalents. People have enslaved their own kind going back as far as slavery is known in ancient Sumer so a superiority of race as singularity is not necessary for an institution of slavery.
But in the form of an economic slavery, what forces one into the cash nexus in the first place? For that matter, what is economic slavery?
That would be where I'd begin to look as it would relate to 20th or 21st century slavery, if that is the term you prefer to use. You may think you see the form best at UPS in one presentation or another because it's the most familiar to you but step back to see the larger picture and that same form is everywhere in one way or another. Does this mean slavery is also everywhere?
But if true, the real question is, how did it become so? Also what is the definition of the term slavery and the origins of it? One origin is hinted above obviously.
I once read that Slavery requires a shortage of labor and a surplus of land or in economic terms, one factor of production imposing on another based on imbalance. In this case the 3 factors of production being labor, land and capital. But taking the same idea above with slavery and just switching land for capital, could the same effect occur? If so, would the slave side appear different only as a result of being under a different name? Under a form of slavery, would a labor shortage today be determined not by numbers of actual workers available but number of actual workers available at a certain price? If yes, does crashing the value of a labor market become necessary when it's (labor) potential to rise above a certain value point becomes evident? Above a certain value point, would labor refuse to work and instead run off to it's own pursuits and desires? If so, would getting labor to remain require a rise in wages to maintain the labor to capital balance?
If Kings of old piggybacked on the first form of slavery as gaining benefit of wealth and power, could a new form of King also do the same under the new form of slavery? Under the new form of King, what would become of his wealth and thus his power if the new form of slaves became economically satisfied with the product of their labor and then ran off to pursue their own wishes and desires?
If a King's power only remained as a result of the benefits of slavery and his slave holders having the right amount of slaves, would the King bestow privilege and benefits upon the slave holders often to the disadvantage of the slave? Would the King from his POV see the slave holder as to big to fail? But slavery ended as institution, right?
What if we determined that the etymology of the term slave even slightly fit modern conditions, could we say then that we fit slavery in some form? If most failed to see their condition as such, even taught to even see it another way, would this make the maintenance of said system easier? Instead of taskmasters and whip crackers to keep the slaves in line, if the new slaves policed themselves as a result of taught belief, would this benefit the new slave holders? Would new slave holders even demand slaves attend institutions that taught the slaves how to think, believe and act?
If true, is it easier now as the so-called slave fails to fully understand it's condition and thus acts as it's own cage?
BTW: If you look up the etymology of the term wage, salary or hourly rate are the same or both are wages. There is no difference. Wage is a value paid based on time, regardless of hour, day, week or month. Those are terms negotiated or given at the time of hire. Hourly rate and salary are just different forms in which wages can be distributed. Hourly rate and salary are not apples and oranges at least in definition of wage IMO.