What does Yahoo do? Microsoft has Windows, Office and Xbox. Amazon has massive web server and product distribution platforms. Apple has OS X and iPhone. Google has Android, search, ads, and an online office suite. What does Yahoo do? I guess they have some long-time email users and a well-liked stock tracking platform?
Google (as opposed to Alphabet) really only has Ads, everything else is just to help get those ads in front of more people more often. In the sense that both Google and Yahoo are mostly focused about showing adds, they are not that different. Google has just more means of showing ads that are more effective, and viewed as cooler by its users.
Actually they have like ~1.37 Yahoos worth of non-ad revenue[1][2]
[1] https://investor.google.com/earnings/2015/Q2_google_earnings...
[2] https://investor.yahoo.net/releasedetail.cfm?ReleaseID=92308...