Hindu sanatan practices were pretty much established by the rulers at the time. The rulers could rape and kidnap women and children, they could confiscate someone's property, they could practice ploygamy, prostitution and also indulge in "Som Rus" while they selected brahmins for their political propaganda and other lower castes for other shitty jobs. The rulers even declared themselves as decendents of Gods...like surya bansi and chandra bansi, and Indra bansi.

The point is, may be Krishna's logic worked around 5000 years ago but not anymore. In a modern day each and every individual has a choice to live like a Brahmin, Chetriya or Sudra. Lets judge people by their actions and not the birth caste and we will be fine.