This is just bombastic and ill-informed.
To start with, Yahoo has >10% of the US search market[1] – down YoY, but nothing to sneeze at. Their sites also see more unique visitors from the desktop than anybody else – >195m in December[2], and that's the sixth month is a row. There are still loads of email users; finance, sport, shopping, everything that legacy portal sites typically had.
Furthermore, Yahoo was never really a good search engine. It was basically a curated directory until it started using Google's search in 2000 or whenever. I think it used it's own crawler for a while, but it's been powered by Bing since 2010 or so.
I'm aware that I live in a bit of a tech bubble — I don't use Yahoo properties, but there are loads of people out there who use the web in a totally different way. Yahoo's got a lot of obvious issues to deal with, but they've also got lots of money and talent; I don't see any reason that they won't succeed with a bit of restructuring and some strong management.
[1] http://www.comscore.com/Insights/Press_Releases/2014/4/comSc...
[2] http://www.cnet.com/uk/news/yahoo-tops-the-most-trafficked-w...