I like that people can’t accidentally bring a loaded gun onto my plane and are deterred from doing it on purpose.
A committed attacker can probably get by TSA, but a committed attacker will also likely flag other parts of the layered defense system that TSA is only one part of. The intelligence apparatus can and does flag specific threats to TSA, which is way better than FBI having to figure out ad-hoc how to screen millions of travelers whenever they think there’s a specific credible risk.