They do still have some smart people, but I don't think anyone or any amount of money can turn things around for them in any meaningful way.
Their pre-Marissa acquisitions were almost universally wastes of time and money. It's too soon to tell about the recent acquisitions, but I don't see them making that $1bn back from Tumblr in my lifetime.
Yahoo is an also ran, constantly playing catch up and trying to emulate the successful behaviors of other companies. The negative public perception of a lot of their services in the technical community is mirrored inside the company, and there is nothing anyone can do to force positive change. Things that Google and Facebook and others announce were projects 3-4 years ago inside Yahoo, that never launched. Once you see that happen a few times, you get sufficiently disillusioned and leave. I don't think for all of Marissa's impact that this has fundamentally changed.
For example: Yahoo employees have to use Yahoo Mail for all of their work e-mail. The web interface only, with ads. It's a great exercise in dogfooding, IF you commit to rapidly iterating on the product to make it best of breed for your employees (not to mention real users). But that will never happen at Yahoo, there is no will to make an excellent product for a technically demanding audience.
Now your employee productivity suffers, which means every other product in the company suffers. Eventually you will have to let them go back to using e-mail the way they want to or they will find a way to screen scrape the messages into fetchmail in order to get back to work.