I really am not learned enough to do justice to the topic at all but I'll give an attempt. From what I've gathered, the idea that post-rigvedic Hinduism became polluted with alien concepts that turned it into a nigger religion is completely wrong, and that line of thought originates mostly from a line of egalitarian Hindu reformers from 19th century India. Furthermore, many of the practices and beliefs in India even in the Kali Yuga have analogs in Pagan Europe among other places, a quick example would be the Godess Kali and Demeter Melaina being equivalents.