"When you think of Yahoo, they had a shot to be what Vox is doing, in terms of taking content and distribution, and really focusing on news, sports, finance — the things that uniquely Yahoo was really terrific at — and really build that whole flywheel," she told CNBC's "Squawk Box."
"But unfortunately because of the breadth of what Yahoo does, they sort of became mediocre in so many properties," she said.
Yahoo CEO Marissa Mayer did her best to turn around the company, but it is now virtually inevitable that Yahoo will be sold, Decker said.
She said in today's media landscape, companies should follow Vox's model of building a multibrand strategy that leverages those names across different platforms, including podcasts and television.
— Disclosure: CNBC parent NBCUniversal is an investor in Vox Media.
— Programming note: Warren Buffett appears on CNBC's "Squawk Box" for three hours on Monday, starting at 6 a.m. ET. From 8 a.m. ET to 9 a.m. ET, Microsoft co-founder Bill Gates, a Berkshire Hathaway director, and Charlie Munger, vice chairman of Berkshire, join the conversation.