Not all practitioners can jump to that highest level. They have to climb, step by step from the physical sphere to reach the spiritual sphere. If it is treated as exercise it is not the fault of yoga but of the practitioners.
B.K.S. IyengarI also say with backbends, you have to be cautiously bold. Not carelessly bold. You have to descend to the dictation of the spine. You cannot command from the brain to do the poses. As you play with a child, guarding the child from injuries, similarly you have to play in backbends, guarding your spine.
B.K.S. Iyengar