Defence in depth is a sound principle. It helps to raise the cost of successful attack, and to avoid single points of failure in your security architecture. I

Defence in depth is a sound principle. It helps to raise the cost of successful attack, and to avoid single points of failure in your security architecture. It mitigates malicious attacks, human error and component failure. You are right that nation states can throw more resources at an attack. All you can do is make attacks as difficult and expensive as possible for an attacker to pull off without detection (commensurate with the value of the assets being protected).