[Strategerist]

Reagan's SDI definitely would and did work, and lead to this technology..

There wasn't the slightest possibility that SDI ever could have stopped more than a fraction of an attack of thousands of missiles, even if the entire GDP of the US had been spent on it for ten years. A lot of the promoted technologies were essentially fraudulent from scientists just looking to get funded.

In terms of stopping a raid BMD defense MIGHT work against an attack of < 20 missiles from Korea or Iran.

No aspect of the current system has been credibly tested under realistic conditions (where warheads employ decoys and penaids, etc.)

Of course then you get into the issue of why it freaks the Russians out so much, which is more complicated.

[Navy Patriot]

You set 1980's developing defensive technology against developed 2010's offensive technology, and conclude that defensive technology is worthless, it is not. It is far better than nothing.

You also miss the entire point of Reagan's SDI. It was designed to use a weapon the Soviets didn't and never could have, and to establish a trust that could be earned by both the US and the Soviets.

It was an unparalleled success.