The goal of terrorism is not to kill people. The goal is to disrupt the normal lives of people and to make them fearful that something might happen. Our lives have not returned to normal since 9/11, so I have to agree with the OP that terrorists have succeeded in their mission of disrupting our lives.
It's been 18 years since 9/11. An entire generation has grown up in a post 9/11 world and know no different. I'd make the argument that how we live now IS the norm.