I think this was the excuse, aside from racial inferiority, that the wealthy status-quo supporters have been using for decades and decades. Culture exists, but I’ve seen no evidence that it just so happens that the culture of the two groups we’ve oppressed the most, by far, (black Americans and Native Americans) undervalues traditional achievement and overvalues underachievement. It seems much, much easier for me to believe that centuries of brutal oppression of these two groups has not yet been eliminated, and some of the ramifications of this oppression are still around today.
If there are differences in culture, they are swamped by the actual oppression and discrimination out there. We couldn’t even hope to see how culture is involved until we have some semblance of a fair society – without things like the Ferguson report, showing that police departments routinely target and mistreat black people; without hiring and housing discrimination; without zoning and public policy that relegate so many black people into neighborhoods with no grocery stores, banks, or other essential services; without extensive and ongoing mistreatment of black boys resulting in massive differences in achievement driven pretty much entirely by how these black boys are treated, aside from income differences; without the widespread denigration and dehumanization of black children in education, including the denigration of African American Vernacular English, essentially gaslighting black children whose only fluency is in AAVE; and much more. Once we solve all that stuff, most or all of which could be addressed with public policy, we can look to see if maybe culture is involved.