Digital ads had the most wow effect at the time of google's text ads and Internet yet not being a general demographics' thing.
Back then, they were able to show numbers, but not now.
First generation internet users were mostly highly technically literate, high income professionals. Now, the user ratio has reversed.
You can argue that putting efforts to find a needle in a haystack was still paying off when the majority of needles were of incomparably higher marginal value than they are now: consumer goods clicks, say, are lower value than commercial equipment sales clicks, yet you still have to put an equivalent or greater effort to datamine somebody to make them buy an accursed face lotion even if the number of face lotion buyers is 1000 times bigger.
This is a tragedy of the Internet ad industry. There is a finite amount of eyeballs, and the amount of companies with a substantial money wanting to sell you a face lotion will always eclipse the amount of companies who market unique, relevant, specialty products one may actually be actively looking to buy.