To me it's actually a simple paradox:
Due to the invention of the printing press, and then the computer the acceleration of information absorption has increased tremendously over year over year comparisons. This means that people have the POTENTIAL to be smarter then before. However, that also means that they have problems like information overload and intellectual dissociative disorder. So that is why most of the "high-tech" world is currently feeling more depression and less empathy towards one another, because they "grew" up too fast. I mean go back thirty years and tell someone you can sit down at a box and know everything there is to know about everything, and they'd call it sci-fi. Now we complain when we aren't use a DSL line.
To answer the question more abruptly, I think that we have the ability to be smarter, our capacity has increased because of our ability to learn more at a younger age thanks to technology, but all in all that has disillusioned us with the world, which makes us want to revert to hedonistic tendencies. That's why I'd guess most of Generation X,Y, and soon to be Z feels lost and buries itself in drugs, sex, and mindless media. They can't help it, they've been given the ability to know everything, but no context under which to envelop in it. I mean do you really think a Judeo-Christian or Islamic, or any other antiquated belief system can hold its own against the amount of knowledge available to your average 12 year old.
I guess that still wasn't a basic answer. Fine then, to put it simply: We have more of an ability to be smart, but we no longer want it, so we dumb ourselves down, fearing that intellect will not make us happy.