Getting back to the original thread topic;
I have been reading about asw and submarine warfare in WWII and believe that the evolution of those technologies are relevant to these discussions.
Both sides developed passive and acitve solutions for detection and countermeasures and both sides innovated new technologies that changed the game for a period of time (Radar, sonar, radar detectors, detection of radar detectors, snorkols, etc) .
Putting Ultra aside, what is key to this discussion is that the ultimate sucess by the allies was born from the integration of a number of technologies, platforms and tactics. The success of the hunter killer groups is the final result in this illustration. Here you see sonar, ship born radar, visual detection, airborn radar, and signal detection integrated into a single force and command structure. Add to this enhanced weapons, improved tactics and combat experienced crews, and the term iron coffin was accurate.
I have only worked in the assembly of parts of the technologies we are discussing here so I am not an expert by any means. What I can say is that throughout the development of a manufacturing process for a new sensor or weapon system, changes were made as testing continued and even more following fielding and use in exercises meant to simulate combat.
In regard to the US / EU defence capabilities realted to "stealth", as long as we field technologies and allow the users to provide feedback, and then act on that feedback, I think the huge research budget advantage currently held by the West will ensure that a combination of evolving systems working in tandem will maintain a distinct advantage. It is therefore irrelevant if a particular system can defeat all detection systems at any given time.