Yes, but probably not for the reasons you think.
We live in an era of instant gratification, yet learning stuff takes time and * gasp * effort. We can’t even be troubled to stop texting long enough to keep our SUVs in our own lane, so what makes you think that anybody will pay enough attention to anything boring like education well enough to have at least the basic math and language skills expected of a third-grader? We have a hard time finding cashiers capable of counting out correct change even when the register tells them how much to give back, so what makes you think any sort of actual higher reasoning like critical thinking is even possible, let alone likely?
Still, even as cynical and uncharitable as I am at times, I gotta go with @Joker94 and say that “most” is an overstatement. I think that if you look at each individual, you will find that there are relatively few actual morons. That said, groups behave differently from individuals, so groups of people can be quite stupid even if all of the people in the group are intelligent.