The basic information about surface warship specifications isn't classified. We know how many interceptor missiles they can carry. Standard doctrine is to fire at least two interceptors at each incoming threat in order to increase the probability of a kill. And empirically these defensive systems work very well, but ships in action empty their magazines quickly and then are out of action until they can return to a friendly base to rearm. At some point there just aren't enough hulls and missiles to sustain the effort.

They've actually been pretty open about the expense and difficulty for a long time. At least since the Iraq war if not earlier.

Japan made public that one of the motivations for continuing rail gun research is defending naval vessels against saturation attacks.

Most powerful navy "failed its mission", as well as Russian navy received heavy casualties, so we have enough public information that modern drones and missiles are highly effective.