To repeat, it's not physically possible to judge every single thing. It doesn't matter if you're literate and engaged - there's just not enough time, even if you were to spend every hour you have on this. And most people have jobs etc.

This is simply not true. Once literate it often takes a minimal amount of effort — back of the envelope calculation or google search— to do a first pass test of the veracity of a source.

You're still relying on another party when you do a Google search, hell if you want to get crazy about it, you are relying that you were correctly taught literacy and that when you read a word, the meaning it has for you is the same meaning the author attributed to that word. It's not guaranteed