I have two significant experiences that explain the imminent failure of Yahoo.
First, I was in charge of marketing research and the advertising for a large bank. I had the funds to try many kinds of advertising and to measure the impact.
I found the advertising budget to be good for one thing: informing statewide employees of new bank programs. It also reassured top management that we did advertising like every other bank and good advertising at that.
I have seen advertising be effective in dealing with the ignorance of tourists and children. Otherwise, advertising is useless; an horrific waste of money.
Second, I have advised nearly 2000 small businesses in the US and abroad. I have never seen one where advertising brought in customers.
This was the basis for a management course I taught in the early 80s and the subsequent book on the subject called Marketing Without Advertising. The first chapter of the book explains why advertising doesn’t work. The book makes a distinction between advertising and listing. Listing is putting information at the point the customer is looking for it. Google meets that definition.
Yahoo has based its survival on standard advertising. That is why Yahoo is effectively gone.
The hundred year sham that advertising works has been refuted by the Internet that allows people to get information before they buy. And ignore the expensive crap that advertisers squeeze in front of and behind everything.