Being worked to the bone while getting paid barely enough to survive affords only a very theoretical freedom and capacity for personal development.
We know this from every UBI pilot ever ran: People do start businesses and better their own situation if you remove them from the threat of poverty and homelessness.
https://amp.theguardian.com/news/2019/feb/25/modern-slavery-...
This is unfair to actual modern day slaves.
Have you missed the following part?
> millions of people who were (and still are!) treated as literal chattel to be bought, sold, separated from family, mutilated, raped and killed at a whim.
If you're comparing the plight of Amazon workers to actual slaves, you're playing down the plight of actual slaves.