I don't think the failure is on Mayer; Yahoo was a walking zombie before she arrived. They were the last remnant of the dot-com boom -- a media company without a significant role in content, advertising, shopping or computing. They had no technological advantage, or really any foundation for a competitive advantage to set them apart from the rest of the market.
Quite simply, Yahoo was culturally never a technology company. They defined themselves as a "media" company in the mid 90s to avoid drawing Microsoft's ire, but they said it for so long they believed it. They underinvested in technology throughout the late 90s and early 2000s, and by that time Google was the behemoth that Yahoo should have been. Yahoo is only around today because they recognized the emergence of China and made a lucky investment in Alibaba. Without that investment, Yahoo would have gone bust years ago.
Quite simply, Yahoo was culturally never a technology company. They defined themselves as a "media" company in the mid 90s to avoid drawing Microsoft's ire, but they said it for so long they believed it. They underinvested in technology throughout the late 90s and early 2000s, and by that time Google was the behemoth that Yahoo should have been. Yahoo is only around today because they recognized the emergence of China and made a lucky investment in Alibaba. Without that investment, Yahoo would have gone bust years ago.