If by "worthless" you mean that someone particularly determined can get a bomb onto a plane, then airport security is, always has been, and always will be worthless. Current airport security is particularly weak surrounding the access that mechanics, baggage handlers, etc have, but as these people need this kind of access to do their jobs there's not all that much that can be improved there. Passenger screening is also fairly laughable, as while they're busy confiscating your water bottle they're still letting plenty of knives and even the occasional gun slip through (there are quite a few recorded instances of people inadvertently having these things in their bag, only to realize it after their flight). And yet despite all of this, we're not having planes hijacked or blown out of the sky left and right, because people going after planes are actually pretty damn rare, the existing security provides a fairly strong deterrent as it is, and good old fashioned police work can nab most of these plots while they're still only in the planning stages.
However, none of this stops people from freaking out (with the help of the government most of the time) every time some incident or near-miss happens, and exclaim "OMG, we're not secure enough. Someone needs to do SOMETHING!" And as a result we get some new security measure that's flashy, inconvenient, and actually doesn't increase overall security in any meaningful way. It's all just security theater, designed to convince folks who don't understand security that SOMETHING is being done.