I feel that "YouTube makes you an idiot" is a misdiagnosis. And one I hear frequently.
Books can make you an idiot too- I think of "Rich Dad, Poor Dad" or "Grit" or any number of pseudo-science best seller books. These books end up capturing the public imagination in big ways too- Grit caused some government policy in the US around when it was popular.
The difference, I suppose, is that YouTube works faster by having many different people presenting the same bad ideas that the algorithm has helped you to buy into.
On the other hand there are amazing and useful YouTube channels that I use all the time like Practical Engineering, Crafsman, Technology Connections, Park Tools, SciShow, Crash Course, and on and on.