but in real action they probably wouldn't work very well

They did work well. The system wasn't shut down because of any lack of capability, it was shut down due to an arms treaty with the soviets that limited the number of anti ballistic missile sites.

We would have a network of ABM sites across the entire country by now if we hadn't signed that treaty, meanwhile other countries like China don't bother trying to de escalate their military capabilities. This is going to bite us in the ass in the near future when they inevitably decide to take Taiwan and completely cut us off from microchip manufacturing.