The attacks on 9/11 did not necessitate a response in force. The attacks were largely due to internal security and intel failures in the gov't. Further, at no time did the gov't ever believe that further attacks even approaching the same magnitude would recur, they definitely would not have a frequent recurrence. Thus, a forceful response was not necessary to the defense of the nation.
Moreover, middle ground was available if we simply wanted to hold those most responsible for the attacks to account. We could have agreed with the Taliban offer to hand Bin Laden over to an international tribunal. We refused the offer and resorted to a war that has now cost the US over ten years of committed resources, thousands of soldiers killed, tens of thousands more wounded to the point where they will never live a life approaching normal, and tens of thousands of innocent civilians killed in Afghanistan.
You are right to say that we ought not have just turned Afghanistan into a parking lot; in fact, we ought not have ever placed one US boot on the ground in that country and, unless we were conducting operations simply to help those oppressed, extorted, and exploited in Afghanistan to get out of Afghanistan, we ought to have left the entire region alone.
A handful of men working with box-cutters and taking over jumbo-jets is not a call to war. It is, rather, a call to individuals to not let your plane get hijacked by a few dudes with box-cutters.