There is no reason to think that Yahoo is a healthy company, since it has been sold by parties.
Verizon bought Yahoo's core business in mid-2017 to integrate it with other properties such as AOL and the Huffington Post.
Until before it was sold, Yahoo had a negative value. In other words, the value in the company's stock market was less than the value of its assets. The most valuable part of the company was the percentage that the company had of Alibabá.
Bad leadership, frequent changes at the top, lack of talent retention, bad acquisitions and lack of product innovation have brought yahoo down. Verizon Communications, the largest telco by market share in the US bought out most of Yahoo’s assets, including their core internet business for a bargain price of $4.48 billion in 2017. Now yahoo is merged in a company called Altaba and after its integration with AOL it would become oath. With the launch of Oath, verizon will have a number of mainstream content brands, such as AOL, Yahoo, MapQuest, HuffPost, TechCrunch and EndGadget all under one umbrella. The oath will empower verizon with its own content distribution for USA. Hence, for last few years the life was bad at yahoo but the vision of oath will definately get the glorious days back