The problem with yahoo was never quality of the traffic. They have the most coveted audiences cornered. Their problem is the lack of good ad units. They have banners... That's unacceptable in 2016.
The yahoo.com homepage used to command some of the highest ad rates on the entire internet, but now you can buy their crappy inventory for a few cents/click, some of the lowest in the industry, even amongst other junk like taboola and outbrain.
But I just launched a yahoo/gemini campaign 2 weeks ago, for leadgen on web. They definitely have more than banners.
(Also, I've found banner ads can refer to either the format [728x90 graphic] or the model [pay per view/CPM/CPV]. They offer the gamut just like everyone else, even the small shady players.
To say that yahoo just has banners is very incorrect.
So not only does Yahoo! run the currently "hot" ad unit (they also do rewarded video), they own it.
The fact that simple Banner ads are no longer acceptable is the reason I use uBlock Orgin....