Some years ago, I read an autobiography by Jim Clayton, the founder of mobile home manufacturer Clayton Homes, now a Berkshire Hathaway subsidiary.[a]
One anecdote in the book stuck with me: In the early days of the business, Jim kept getting pestered by salespeople from the Yellow Pages, who told Jim he would benefit from advertising in the Yellow Pages to attract new customers.[b] Jim decided to run a test. He ordered and installed a new red phone in the office, ordered a new phone number just for the red phone, and bought a big ad in the Yellow Pages listing only the line that rang the red phone. The ad ran for a year. No one ever called the red phone. Jim never again spent a cent advertising on the Yellow Pages.
By then, the only consumers and businesses who actually searched the Yellow Pages for products and services were those who didn't have a choice, e.g., out-of-towners needing a plumber who couldn't get the name of a trustworthy plumber from a trusted neighbor.
As regards Google, as its search results and rankings become less trustworthy, more and more people will stop using them to find products and services. Other platforms will benefit, like Reddit. And advertisers will follow, as always.
--
[a] https://www.amazon.com/First-Dream-Jim-Clayton/dp/0972638903...
[b] The Yellow Pages were in essence a low-tech printed-paper version of the search business. Businesses paid to advertise in a thick yellow book, and consumers and businesses searched the index of that book to find products and services. See https://en.wikipedia.org/wiki/Yellow_pages