I think that this is an application of the changing circumstances argument to culture. For most of human history the challenges faced by cultures were along the lines of "How can we keep 90% of the population working hard at agriculture?" "How can we have a military ready to mobilize against threats?" "How can we maintain cultural unity with no printing press or mass media?" and "How can we prevent criminality within our culture?"

Individual rationality does not necessarily solve these problems in a pre-industrial society better than blind duty, conformity and superstitious dread. It's been less than 200 years since these problems stopped being the most pressing concerns, so it's not surprising that our culture hasn't evolved to create rational individuals.

Cultural evolution is also an answer to

(Note: it's unclear to me how the category of "evolutionary restrictions" could apply to rationality techniques. Suggestions?)

Education is still showing good progress - as manifested in the Flynn effect.

I thought a lot of that was accounted for by nutrition and other health factors — vaccination and decline in lead exposure come to mind.

It's been suggested that the Flynn effect is mostly a matter of people learning a kind of abstract reasoning that's useful in the modern world, but wasn't so useful previously.

There's also a broader point to be made about why evolution would've built humans to be able to benefit from better software in the first place, that involves the cognitive niche hypothesis. Hmmm... I may need to do a post on the cognitive niche hypothesis at some point.