I think part of the lack of response has to be due to the world wisening up a bit when it comes to mid-east policy. It's not sufficient to just cowboy in there and create a power vacuum by ousting regimes we don't like, and we're starting to give due consideration to the complicated ethnic and sectarian mosaics of the area.
The fight against ISIS has to start as a cultural one, and we have to be careful not to let it lead to generalized Islamophobia (which will just end up hurting the cause altogether). They already feel like they're apostates, we don't need to give their argument more material than it deserves.