You need to consider what threat you are defending against.

Before credit cards were popular, it was common for aircraft passengers to be armed with handguns and carrying a lot of cash -- yet there were few incidents. Think about that.

An organization planning an operation against any nation-state relays on secrecy and anonymity to function, period. That is what random screenings will help combat.

The current TSA regime is really trying to stop crazy people. I believe there is some documentation to establish that they are somewhat successful at that too. The problem with the TSA approach is that they are too big to be competent at what they do, and the near universal contempt that they are held in hurts that mission -- even deranged people hunk the TSA is dumb.