1) Adversaries are generally as lazy as the rest of us.
2) Adversaries (no matter how advanced) have to follow the laws of reality.
What do you think the path of least resistance and cost is?
It means do good proactive architecture and threat modeling to figure out your vulnerable points and likely attack pivot points.
It also means do defense in depth to detect and deter adversaries at as many kill chain stages and segments as you can.