> What happened with the idea that ads were a means you had to get to know useful products?

It died a long, long time ago.

This guy, Freud's nephew, is what happened: Edward Bernays [1]. As covered in Adam Curtis excellent documentary on the subject of the history of propaganda and advertising "The Century Of The Self" [2].

[1] https://en.wikipedia.org/wiki/Edward_Bernays [2] https://en.wikipedia.org/wiki/The_Century_of_the_Self

> If all ads were banned forever from existence, how would anyone discover anything new?

By word of mouth. I know, not a novel idea, but it seems to work quite well on this very website!

The fallacy is that ads were never informative anyway.