It matters at companies with high levels of south asian representation, for example Apple, Cisco, Google, etc. When people complain of caste discrimination they aren't talking about it coming from white folks like you.
But also, "castes aren't based on anything real and are obvious bullshit" (paraphrasing the original comment) is not going to be obvious to everyone and not a very helpful statement. Kind of like saying "the world really isn't flat" -- we know, but it's not gonna help anyone because you're not going to stop flat earthers from existing or being sincere about their beliefs.