It clearly has been working, in fact

Mosul is the result of Obama's strategy. How long has the fight been going on there? 12 months? Worse we left the back door open and lot of ISIS fighters fled and attacked and took over areas of Syria. Driving them from place to another isn't a great idea.

The rapid capture of Raqqa is the result of Trump's leadership.

DAVID IGNATIUS: I’m going to say something that in some ways is sympathetic to Trump. As I traveled across Syria, meeting with Syrian fighters who were trying to take down the regime of Bashar al Assad, every time the name “President Trump” was mentioned, there were cheers from the audience. One Syrian Kurdish commander used a vulgar term, in Spanish it would be cojones, to describe what President Trump has got and why they like him.

More seriously, the big attacks that have taken place around Raqqa, one in particular, a surprise landing by helicopter, I was told by the top US commanders, would not have taken place if it hadn’t been for President Trump’s decision to delegate military authorities down to the level of command. I mean, under Obama that would have taken a couple weeks of White House meetings and then they still wouldn’t have made up their mind.

http://www.cnn.com/2017/07/04/middleeast/us-backed-forces-breach-wall-in-raqqa/index.html