It's pseudo-science, designed to let complacent readers validate their prejudices, and pat themselves on the back.
I have never understood this particular criticism of the work. It is, if anything, an extremely strident argument against prejudice. The entire point is that differences in current day development are not due to innate deficiencies in the people but rather at least in part due to historical quirks of geography and ecology and therefore current development level says very close to nothing about the intrinsic potential or capabilities of anyone from any region of the world.
It turns out that there are lots of readers out there who wilfully confuse "is" for "ought". Even when an author goes out of their way to emphasise that they are only describing their view of reality, not in any way assigning virtue to it.
Then there's some very few left-wing critics who hate it for basically the same reason, but with opposite sign, since it implicitly also rejects that western civilization or the white race is uniquely evil.
Then there's some grumbling from academics who hate a popularizer for all the reasons you'd expect.
Not at all.
It actually plays into one of the most popular prejudices in the west.
Here's how you know if you have that prejudice. Do you think "I'm not like those people."