The nice thing about books vs. YouTube is that it's much easier to critically interrogate books while you're reading them. That was the difference with my dad: he thought about what he read. He repeats what he listens to on YouTube.
I hate the proliferation of audiobooks too, by the way. It's the exact same problem.
To be fair, even reading 'good' books won't make you smart. I think the key is to be critical, which should be thought at a young age. Ikram Antaki dedicated most of her last years in teaching this in Mexico.
Anecdote: When I started studying economics I really agreed with a lot of what I read from economists like David Ricardo, Marx, Smith, etc. Then, I studied what other economist had to say and I could see how they disagreed with the former. This made me realize that I agreed with those people because their arguments 'made sense' to me, but that doesn't mean that what they said is completely true. This is something that has stayed with me, I always wonder how can something be wrong.