Yes, that's kind of my point. We all are brainwashed, from Day One. You don't have a choice which ideas you're exposed to when you are a child.
As an adult, though, you can start to exert control over the narrative. You can explore ideas that your parents and school didn't share with you. You can pick up a book, learn what you want to learn, share ideas that were previously off limits.
Mass media (esp. doom scrolling) attempts to regain control of that narrative. And, yes, of course, mass media's job is to insert new beliefs. Why else would I have an opinion on Israel, a country I've never been to, that has no immediate relevance to my life? Why don't I have a similarly strong opinion about countries like Kiribati or Abkhazia?