The seeming counter solution is simply this: smart people should BREED!
If we did that, we wouldn't be making smart decisions.
So many stories, so little time.

You are correct when I first saw this (years ago, when it was entertainment and less of a documentary), my husband and I nodded our head at the notion that dimwits do tend to seem to knock them out a lot faster and with less regard than those who are more careful with their decisions and money. The idea that eventually, the dim would outnumber the intelligent is fairly credible. There will always be intelligent people - some are just born to it. It's what opportunities they have to share their smarts for the good that steer us in a better direction. Apparently - our ship as veered off course for some time now.