The movements in Kung Fu forms are graceful, just as the movements in ballroom dancing, synchronized swimming, or ice skating are graceful. However, graceful does not translate to useful. If any of this was effective, you would think at least ONE Kung Fu "master" would be a world champion boxer, ultimate fighter, football or basketball player, etc. As demonstrated in so many combative sports and other physical endeavors, basic hard, linear, focused, controlled, and powerful movements are much more effective than soft, circular, "beautiful" movements. As a performance art, Kung Fu is beautiful, as a combative art, it is more hype than substance. No Kung Fu master of any time in history could stop Mike Tyson or Chick Liddel with Kung Fu techniques.
Extreme flexibility is genetic, not trained. A normal person can train and increase flexibility, but extreme flexibility requires extremely elastic ligaments. During the Cold War, communist countries tested children, found the ones with special genetic abilities, and then forced trained the children to exploit these abilities in the Olympics. In Kung Fu, Yoga, and such, thousands of children are force trained at a young age, and then the ones with extreme flexibility ability, or some other special ability, are selected and trained to become "masters." My question is: what happens to the ones who have average genetic composition? What are they trained to do, or are they just discarded?