Hot take: I don't think social media made people dumber. We've been dumb this whole time. It's just that you used to have to have a job that people sent their dumb letters to, to notice. This made "Engaging with fools" an occupational hazard rather than the 24/7 experience it is presently.
No matter how bleak things may seem, just remember that in the 1960s the US Coast Guard received reems of earnest letters begging them to save those poor castaways on Gilligan's Island.