It's very difficult to come up with a plan. As of now, most of 'our' work done is by the hands of rebels. And those rebels fight against other rebels too. You have groups like the Kurds who fight against IS, but are bombed by Turkey. Then you have Russia fighting against IS too, but also take out some rebel groups who appear to be supported by the US. Not so long ago the US send planes to stop the Russians from bombing 'our' rebels. And not to forget, you have Assad who might be protected by the Russians, for whatever reason. It's all pretty vague and you can't just nuke the place because of all the parties that have shared interest in the region. Like how IS makes money, someone is buying their oil, and someone is supplying them with guns, clothes, food etc. It could be Iran, could be Saudi Arabia, whoever it is, IS has been backed by some big important leaders.