The delay isn't about just about technical countermeasures. It's about giving time for other options to work. These could have included: engagement and diplomac

The delay isn't about just about technical countermeasures. It's about giving time for other options to work. These could have included: engagement and diplomacy, regime change, or direct action. In addition, by increasing the cost of developing these systems, you force hostile (or non-friendly) governments to split their resources. Every bit of funding that went into building a rocket is a bit of funding that doesn't go to Quds Force.