seems like you agree with her in part.
we don't know what genes are responsible for what capabilities and we can't just wish that away by ignoring it.
No, I don't agree with her at all. In-group diversity is FAR larger than between-group differences, to the point that it would be idiocy to stereotype by group rather than distinguish by individuals.
We do understand what genes are responsible for what capabilities when it comes to simple shyt like height, skin color, hair color and texture, etc. Those traits are mostly determined by just 5-10 genes, and thus can change rapidly across a population based on just a few base-pair shifts. Whereas the genetic basis of shyt like personality and intellect is far more complex and based on the variable interactions of many hundreds of genes, for which any particular base-pair shift has only the smallest impact. Thus evolutionary change in those characteristics is very slow and difficult to select for.
Scientists believe that the basic genetic intellectual capacity of the human brain was set about 50,000 years ago. Two thousand years of genetic isolation is comparatively meaningless.
Not to mention that the very nature of caste marriage rules tends to keep natural selection from having any meaningful impact anyway - once caste becomes the most important factor to a marriage, you're helping to ensure that everyone in the caste ends up getting married and producing children, and thus you aren't selecting for any evolutionary traits anymore. All of the castes would retain the same genetic potential they started with 2000 years earlier. At the most you might increase certain genetic deficits due to inbreeding, but that would only happen if the genetic issue was already present within the caste to begin with.