William Gibson famously said, "The future is already here—it's just not very evenly distributed." It's easy to imagine a science-fictional fantasy world where everything is made of diamond and plastic, and literally everyone has their own brigade of robots, spacepacks, and jetcars to do their bidding, but as Gibson points out, the real world doesn't actually work like this: there's nothing contradictory about the high technology allowing you to read this post existing in the same world where millions of others are starving, thirsty, and illiterate. The Earth is just a very big place compared to what we know how to imagine personally; the wealth and wonders that exist in some places, don't exist everywhere. As long as this is true, we should expect variance in wealth to increase, as new toys for the rich get invented faster than the basics can be provisioned for everyone; Carlos Slim can purchase extravagances that hadn't been invented in the days of Cornelius Vanderbilt, but dying of malaria is the same as it's ever been.
A similar thing could be said about knowledge and ideas. Human civilization has been rapidly accumulating knowledge, but we're not getting proportionately more capable as individuals. People typically don't have the resources or inclination to learn deeply outside of their own specialties, and many never get to master any specialty at all. There's nothing contradictory about our brightest scholars seeing more deeply into the true structure of the world beneath the world than the uninitiated would have ever conceived possible, while at the same time, the masses labor under the most primitive of superstitions. As long as this is true, we should expect variance in knowledge to increase, as the cognitive elite continues to advance the frontier of the known faster than the basics can be taught to everyone; our master biologists know more about the nature of life than their analogues in the days of Darwin and Wallace, but to the proletariat, "God did it in six days" probably still sounds like as good of an explanation as it's ever been.