"Lack of judgment"?
"Lack of knowledge"?
"Unintelligent"?
"Mental slowness in speech or action"?
Perhaps, "Lack of education"?
In a lot of the points, the author uses "smart" as the opposite of "stupid". Smart is also a vague word that comes up with multiple definitions such as "having or showing a high degree of mental ability", "stylish or elegant in dress or appearance" and "appealing to sophisticated tastes".
I have read the article multiple times, and it seems to me that it fires in all directions. It addresses environmental cognitive issues (air quality, etc.), education, political polarization, etc. In short, it lumps multiple issues under a personal interpretation of a vague (and rude) word.
I avoid the word "stupid". Not only is it vague but it is ableist because it creates and enforces systemic and institutional bias.
Is a lack of education the same as having temporary cognitive issues? Is it comparable to having a condition which decreases someone's cognitive ability permanently? What about people who are unable to grasp social intelligence? What about people who take beneficial drugs that happen to have mental fog as a side effect? Where is the line? To me, the answer is no. Those are all unrelated social issues that need to be addressed separately.