I am thinking that the problem with yahoo is that most likely Mayer doesn't have much faith in the present crop of developers/managers. Recently she did a lot of acqu-hires, because traditionally really good developers are less likely to join Yahoo over better choices.

Maybe improving existing products and making new impressive products are in the plans for Mayer, but to get there she needs capable people and she needs to make Yahoo seems like a good/profitable/fun place to work at.

For a long term sinking ship like Yahoo I think major changes in direction will need some time.