That's not true. Old-school disinformation platforms like TV, bought political parties, etc., worked and still work fine for disinformation and division. If you're not familiar with the subject, you'd be surprised just how inventive these campaigns can be.
There is an interesting book called 'Not Born Yesterday' that points out that people are pretty skeptical .
https://www.goodreads.com/book/show/45358676-not-born-yester...