To grasp the underlying principle of any technique we have to change our thinking in two ways. First, we must realize that every technique can be broken down into basic movements. Basic movements are like the letters of the alphabet. From a knowledge of the letters and how they are used and combined, we make words. From just the 26 letters in the English language more than half a million words can be formed.
Words become obsolete.
New words are constantly being made. But, the underlying letters do not change. Fighting is equally dynamic and alive. It changes with every generation. Techniques become obsolete.