Where has this myth come from that the other Arab states don't care what IS does and are doing nothing to keep them in check?
In September 2014 leaders of Egypt, Iraq, Jordan, Lebanon and the Gulf Cooperation Council - an alliance of the Sunni Arab Gulf nations, including Saudi Arabia, Qatar and the United Arab Emirates – pledged to “stand united” against “the so-called Islamic State in Iraq and the Levant.”
In a document known as the Jeddah Communique, issued after intense diplomacy from US secretary of state John Kerry in the Saudi city, the signatories agreed to staunch Isis funding and influx of foreign fighters, critical priorities for Washington. They expressed openness to contributing directly to the war effort, saying they would be “as appropriate, joining in the many aspects of a coordinated military campaign” against Isis.