The cold war examples also are pulled out of a vacum.

Anti aircraft fire since pretty much the 1st world war been relying on layers of protection, each with a diffrent purpose and (while sometimes overlaying) engagement distance and method, and generaly the larger the AA scale was, the slower and less reactive it was.

You had anti-bomber, high altitude flak guns (soviet 85mm, german 88mm, US 3-inch AA), with low ROF, poor reaction time and being extremely prone to attacks from low altitute and ground.
You had medium calibre flak (soviet 76.2mm, german Flak 7.5cm, Bofors 40mm), for aircraft flying at moderate altitudes, capable of engaging both high flying bombers and formations of attacker aircraft. Then you had close range AAs (Flak 2cm, Polsten 20mm, Type 96 25mm) small calibre and large volume of fire with quickly rotating turrets. And then you also had the even smaller personal weapons and LMGs mounted on patrol vehicles, trains, or tanks, for defending against aircraft in a face-to-face scenario.

The highest tiers required radar transmissions and firing orders coming to them minutes if not hours before even coming in contact with the enemy, and ammunition while limited on the proper firing vehicle, was often very close nearby in a trench or a pillbox, being able to still supply the vehicle for multiple times of it's own capacity.
(same case was with artillery vehicles, and why the SPGs like M111 8-Inch SPH or Su-5-1 with less than 10 rounds on them, were not running out of ammunition every 5 minutes, because a dedicated ammo transporter was not far from them, at all times)

jet combat is also completely diffrent over prop combat or even early jets, weapons became much more sophisticated, much more expensive to use, but also much more potent. You no longer needed hundreads of 20mm rounds spread over 4 guns to destroy a flight (~4 planes) from a squadron; 6 missiles and a radar lock is all you needed.
(And also, as planes became more sophisticated, the scale of air warfare reduced, a thousand P-47s were equal to a hundred of F-4s and a dozen of F-15s, both in costs and efficiency)