Critical thinking is taught in schools. The issue is it's rarely applied. Critical thinking takes a lot of mental effort and often boils down to who do you trust.

A group of flat earthers designed an experiment to test their belief. Performed it and showed the Earth was round. Then dismissed the result.[0]

When your priors say the probability is nearly 0 then no evidence is strong enough to change your belief. It's why science sometimes only advances when people die.

[0] - https://brain-sharper.com/science/flat-earthers-tried-prove/