Kung Fu shares one primary characteristic with many other physical pursuits such as Western Boxing, Yoga and Flamenco in that they are all essentially creating an art from waving the limbs around in a prescribed fashion. Each one can be a path of self-discovery and improvement through perseverance, dedication and effort. In that respect they can all be Kung Fu as Kung Fu translates as to achieve merit through hard work. Each one utilises a different medium however, be it sport, meditation or dance and if you mentioned any one of the three examples above to your average person then I'm pretty sure they would have a rough idea of what is involved.
When people watch traditional martial art forms in practice it can sometimes be less clear what the goal is however, it's just waving your arms and legs about in thin air. The movements do not fit into peoples preconceived ideas of how fighting should be, the generic punch-punch kick-kick. It is because of this ignorance that people sometimes do not give traditional martial arts the credit they deserve. The moment a martial art becomes a sport the guts are removed from it to prevent serious injury to the competitors, all the parts which make it effective as a form of self-defence. With self-defence there are no rules, weight categories or referee and anything could happen at any time. The forms of traditional martial arts simply teach these principles and develop the accuracy required to make them work.
Far from being a rigid way of fighting, forms practice teaches the principles in a format that is easy to remember and perform. No requirement for a special outfit, gym equipment or a watch. With consistent practice the body begins to assimilate the principles through muscle memory and learns how to make strong and efficient shapes. Once the body understands this, complete freedom of movement can be attained as the principles of movement are so ingrained in the muscular memory. It can be seen as similar to buying a Lego kit. By following the instructions you learn the principles of how Lego works and are able to build the pirate ship as pictured. Now that the principles are understood you can dismantle the pirate ship and build whatever your imagination will allow dependent upon the bricks you have. Each form in traditional martial arts is like owning a separate Lego kit with each one introducing new building bricks which introduce new principles. With time you have enough building bricks to construct something huge and truly creative. So long as the principles are adhered to it will work.
Waving your arms and legs about in traditional martial arts is therefore just a tool to teach the body how to move. Without having to worry about which part of the body you should work on today, simply practice the forms and you will be working your strength, flexibility, control, precision, skill and mental fortitude to mention just a few all at the same time.