Well first a little introspection before jumping to question something so huge. Did you take time to learn the basics? Was it a fluffy (or something that is both impossible and ridiculous) spell such as being transformed into something non-human? Did you color co-ordinate with your intentions and work with the moon phases to enhance your outgoing intentions and energies? What did you use? Do you believe in yourself and have the confidence to cast said spell? Does your level of experience and knowledge match the difficulty of the attempted spell? Did you concentrate? Were you grounded? Were you clear and concise in what you wanted? Have you given time for the results to manifest?
Try asking these before questioning something that has been practiced successfully for more than a hundred years in multiple faith and belief systems. Have a good day and think on all this please.