As a long time Yahoo mail user, I was very disappointed with Yahoo under Mayer. Firstly they did a terrible job with the Yahoo mail web client; it became slow and clunky and inherited the worst parts of Gmail and none of the good parts. Secondly my account was hacked and to this day my old contacts still receive spoof emails from "me" (though not actually my email address) about weight loss supplements.
I am ashamed to tell people my email address. I started moving to Gmail.
Yahoo and LinkedIn are basically right next door to each other and employees from one routinely hop to the other, so it makes sense that they share production values.
Core Yahoo was actually worth a negative amount when comparing its market cap to the market cap of the Alibaba assets.