To everything, there is a season, and a counter-counter- measure to every counter-measure.
Duncan Sandys, after dabbling in anti-aircraft rockets during the Blitz, announced their primacy in 1957. He was premature. Unguided rockets are inaccurate, and guided rockets were judged developed long before the fact. They must be fired within their envelope and are subject to countermeasures.
Bomber intercepters were heavily armed and armored to fulfill their task. Their performance was sufficiently degraded to enable escort fighters to attrit their numbers adequately.
Mosquitos and Arado 234s were fast and hard to intercept, but could be intercepted. The XB-40, a modified B-17 with extra guns and armor, could be shot down. B-29s flying at max altitude could be shot down by Ki-44 and Ki-45 intercepters, enough to make aces. Fast, or heavly armed and armored, both were not invulnerable.
Winston Churchill believed there were ships which were torpedo-proof, and that battleships with deck armor were "proof against aerial attack". He was mistaken.
Battle cruisers and pocket battleships were supposed to out-shoot smaller ships and out-run larger ships, making them ideal. A mistaken concept.
Il2 Sturmoviks were made of armor and totally immune to small arms fire. 37,000 were built. The numbers built were for the purpose of replacing those which were destroyed. Tough, sure, but still not invulnerable.
The F-117 was invulnerable until it was no longer invulnerable. The B-2 may be invulnerable, but remains untested in a high-threat environment. Certainly, it's price tag should make it invulnerable.
War is heck.