Yes, flexibility of body and physical perfection for Yogasana is important. However more important is the state of your mind, Meditative mind. Your flexibility might be excellent but if your mind is not attentive, you are merely doing some physical exercise, not Yoga.
B.K.S. IyengarIgnorance has no beginning, but it has an end. There is a beginning but no end to knowledge.
B.K.S. Iyengar