- Argentine forces carefully analyzed their target, studied, trained, practiced, and drilled for the attack. Over and over and over. Almost as if they believed there was a real war on, and actually wanted to hit an enemy with their weapons...
- British forces mostly couldn't be bothered to analyze their defenses for weaknesses. Let alone train, practice, or drill. Then they footgunned their best warning system, and didn't realize they were under attack until human-eyeball lookouts saw smoke from the rocket motors of the incoming missiles. Once warned, the bridge officers basically sat on their hands and gawked. (Vs., say, alerting the crew. Or trying to use some of the various anti-missile defense systems that the ship had.)
- The ~5,000 ton "warship" was designed so poorly that one modest hit knocked out both her electrical and fire-fighting systems. Even back in WWII, having redundant critical systems was a well-known and much-valued feature of all real warships.
- Hours into the crew's efforts to fight the fires (resulting from the missile hit), coordination and command of the fire-fighting efforts were somewhere between underwhelming and non-existent.
Blunt Summary: The aircraft, missile, and anti-missile technologies used (or available) during the attack on the HMS Sheffield were no more than costumes and props in a play. The real meat of the play was a human story that would fit quite comfortably into the Old Testament. On one side was a small group of skilled and determined warriors, intensely focused on winning. On the other side was a crowd of clueless noobs, wandering through the scenery and telling themselves that they were a real army.