The practice of Yoga is not solely about the flexibility that your body gains. It is also about the feeling of liveliness within your body that you experience during practice. Otherwise, all Yoga practices would become a ritual and nothing more.
Flexibility is something that you gain with time through Yoga practice. It is, however, not the goal of Yoga but simply an added benefit.
Flexibility alone simply means that you can stretch your body more than the average person. It does not mean that you are a better yogi. If that were the case, the people from Cirque du Soleil would be the best yogis of all.
Yoga is about the amount of presence that you bring to your practice, and ultimately this presence should penetrate all areas of your life.