To make it sound like there's no counter to it at whatever the level you may want to clarity for yourself would be incredibly dismissive and inaccurate, when you realise the whole Western vs Soviet/Russian air defence doctrines revolve around cost-effectiveness vs saturation attacks!
It's dismissive because the concept is ridiculous, and no sound doctrine has ever revolved around it.
You mentioned layered defense in the Naval realm, but US Naval doctrine follows the principle I outlined: It's the Strike Group's (airwing + destroyers + subs) responsibility to neutralize the launch platforms, while keeping the CVN as far away as possible. This is because the group's onboard SAM+Phalanx layers can
always be saturated. They only exist as a last resort. It's simply incorrect to say that the doctrine "revolves" around them.
The layered defense is also not "cost-effective" either. I could give you 10 billion USD to layer your carrier group with SAMs and Phalanx systems, while I get 10 billion worth of coastal AShM batteries that I'll ripple if you come anywhere close to my territory. You have no realistic chance to defeat this saturation attack with a 1:1 cost ratio that "revolves" around SAM/Phalanx layers. Your only shot is to neutralize the launchers. There is no other option. And that's what the doctrine actually revolves around.
And we're not even talking about 21st century AI enabled threats here, which have made defending even harder.