datsci_est_2015 explains it better than I would just a few comments down, but this isn't what I mean. I mean that people who are semi-literate or illiterate are terrible thinkers. They are, in fact, fundamentally incapable of understanding the modern world they find themselves in and are CONSTANTLY taken advantage of.
Bad thinkers make bad decisions, and are vulnerable to being manipulated in ways that good thinkers aren't. Try getting a mortgage or a car loan when you can't read complete paragraphs. Try investing your retirement properly. Try doing just about anything that modern adults are required to do. You're definitely going to pay a "stupid tax" throughout your entire adult life if you lack the ability to read critically.
People bemoan the death of journalism, but it's not the journalists fault. Did you know that USA Today was intentionally invented to be an alternative news source for people who couldn't read well? At the time it was bemoaned as the end of western civilization. Now it requires more of it's reader than the places people actually get their news from (Tik-Tok and Bathroom wall graffiti presumably).
FWIW - One side is objectively worse than the other, but it's not by a wide margin (a few basis points if I remember correctly) and it's probably just because one side lives in states that love to take the education budget and blow it on "more important" things.