“Is CAPITALISM just a MASKED form of SLAVERY?”
The main thing to back up and realize with questions like this, is that “capitalism” is NOT an intricate, thoroughly crafted, comprehensive and specific practical socio-economic operating system.
It is a general concept only.
In execution, it can be shaped into anything from a class-based mechanism to keep social strata in place, to an equalizing force in the society, to a cover story for corrupt gangsterism.
There is no slavery inherent to capitalism, but then neither is individual freedom an inherent element of capitalism.