As long as companies can measure a return on ad spend (ROAS) of >1, their ads are delivering value and they'll keep spending. The book you're naming seems to be

As long as companies can measure a return on ad spend (ROAS) of >1, their ads are delivering value and they'll keep spending. The book you're naming seems to be saying that they can't actually measure ROAS. But that just seems... out of touch? Clicks are tracked from the ad, to the storefront, to the buy button, to the final exchange of money; it's pretty measurable. A ton of internet-only brands get almost all of their sales just from advertising -- are the dollars in their bank accounts lying to them? Of course, there's the fantasy that events like IDFA deprecation will make the ad market crash. Spoiler: IDFA deprecation has been more of a blip than a bomb. Advertisers rapidly found ways around it (whether those ways are in TOS compliance or not). Then there are the brands coming into the space just looking for impressions -- think of your old school giants like Coca Cola. They're already comfortable with fuzzy, somewhat unknowable returns. Haven't read the book but I have close contact with multiple people in the industry. And as I said, their results are right there in dollar signs. (For the record: I'd love to believe the ad market actually is threatened, I'm not arguing for it and personally I block ads.)