An interesting point about yahoo is that the actual search engine has never been made by yahoo. It used to be outsourced to
AltaVista and now it is outsourced to
Google
That means in terms of search features the only thing yahoo had were the catergories which are organized by actual people, but are sorely out of date and contain little information.
The only place where Yahoo has really stood out and made anything of worth is in its other features such as mail and games.