Shooting a hole in a bulletproof vest with a slingshot is not a sign the bulletproof vest is garbage. All shooting a hole in a bulletproof vest with a slingshot means is someone decided to shoot a bulletproof vest with a slingshot and found one or more weak points in the bulletproof vest.

Sounds pretty stupid, right?

Okay, now replace slingshot with tank.

Now it does not sound so stupid.

Turns out you can learn something based on the effort needed to breach a defense.

As it turns out, the entire commercial IT industry is basically incapable of stopping small teams of moderately skilled attackers as has been demonstrated to death. A team with just 1-2 M$ of resources is basically unstoppable even with 100 M$- 1 G$ budgets. That is the definition of gross inadequacy.