I'm not going to argue we didn't get what we needed. What we got was a mutant hybrid that may not be producing no better an outcome than the old system. A lot of people recognized the old system was a large, potential security hole. Low paid, under trained people with no job security are ripe for social engineering. Trained, reasonably paid, people with a measure of job security are less likely (although not immune) from social engineering. Professionalizing screeners should improve the situation from that end. Having national guardsmen standing by screening checkpoints was a reaction. Improving the screening process seems like a logical, even necessary idea. Hopefully, the combination of decent standards, training, and professionalism would lead to a better outcome. It hasn't and no one is arguing that.
Second, if someone does try to hijack a plane and the hijack is foiled, or just downs a plane, you will have people questioning the safety of air travel. When Richard Reed tried to light is shoe on fire, or Abdulmutallab tried to ignite his underwear, people questioned 'how did they get on the plane, in the first place.' The next question is if they can get that on a plane, are planes safe? Should I be flying? People are horrible and judging risk and even if the odds of dying from dozens of other, more realistic, events many times more likely than dying from a terrorist attack, they will react by not flying. Airline safety isn't so high because of the altruism of the airlines or the aircraft makers (although many care very deeply about the safety of their products) but because airline crashes are bad for business. Even as rare an event as they are, they cause people to not fly.
Having passengers and crew overreact because they feel that security is 'up to them,' is not a good idea. Passenger reactions are important, but only after all the other mechanisms failed. Simple screening of passengers seems like a perfectly reasonable idea. Applying technology, such as sniffing for organic materials (explosives) seems like a perfectly reasonable idea. The problem is the execution of these perfectly reasonable ideas has been a disaster. I wouldn't say a complete and total disaster, but, it's not a 'win.' The larger problem is the political intransigence that will saddle us with this mess for many years to come, and maybe even exacerbate it.