>I feel that "YouTube makes you an idiot" is a misdiagnosis.

Signal/noise is much worse (arguably books are catching up thanks to LLMs)

People see emotional signals in youtube videos. They respond to vocal tone, facial expressions, these are known to circumvent critical thinking. Like if you examine crowds of science deniers the usual commonality is that they are having a parasocial relationship with a bunch of youtube creators who are nice to them and reinforce their beliefs. The actual content of the belief is irrelevant, if you are disagreeing with the belief, you are attacking their tribe. Not limited to science deniers either, you get this hacking of human tribal psychology even in stuff like people who watch computer game videos. They pick a few champions of their tribe and follow them without critical examination of the content. At least with a book, while this is still possible its much harder. Its also telling that a lot of cranks who published junk science have all migrated to youtube.

I dont think youtube makes you an idiot, so much as youtube content is designed to bypass your critical defenses and overwhelm you. It develops into a blind spot. People can be perfectly rational in most areas and then suddenly burp up some absolute nonsense they caught on youtube.

Oh and the best part, is when you point this out to someone they tend to go "Oh yeah that totally happens... except for my favourite youtube channel which does x and y and z and yes of course I buy all their products and donate to their charities"