The system is not broken. The CA system is not designed to prevent mid-airs. It is designed to prevent controllers from getting distracted. To relate it to TCAS, it's more like a TA than an RA. When it goes off, the controller has to verify that at least one of the pilots is maintaining visual separation. It would be really hard to make a system that is sensitive enough the distinguish an actual potential mid-air vs. a plane that is pointing at an aircraft on a parallel runway but is going to turn final before they actually hit.