There is nothing wrong with STEM for developing critical thinking. You make the claim that American education used to spend more time directly training us to be citizens but that's not true either.
You blame the internet but the rise of anti-intellectualism, for instance George W. Bush, was well before social media.
You blame the decline of experts but that was much more deserved then you let on - see the book Twilight of the Elites. The experts were not just making mistakes - they were completely out of touch.
Twilight of the Elites explains that this was not in spite of rising education, but because of it. Elites used higher education as a bulwark against having any practical experience.