Completing a creative writing programme can help you push your creative boundaries and develop your unique written style and voice. However, pinning concrete outcomes is difficult, unlike taking medicine with a direct professional pathway. In contrast, creative writing does not directly lead to becoming a successful author.
You can become an accomplished, even a great writer without a MA in the subject, but studying at postgraduate level will help speed up that process and provide a framework to develop with like-minded individuals. Sometimes a deadline can help produce prose worthy of greatness. Taking an MA can also make you face criticism and critical feedback in a safe environment- something that all published writers will have had to go through. All these things can help hone and develop a writer’s craft and increase an individual’s chances of success.