Let's be honest, a large majority of charts follow convention, if not transparently in the case of a straight "I Got Rhythm" changes or blues, but more opaquely

Let's be honest, a large majority of charts follow convention, if not transparently in the case of a straight "I Got Rhythm" changes or blues, but more opaquely with substitutions or variations of predefined changes. This is true with jazz and even more so in pop music. A trick I always use it to transpose into a common key and watch the overlap develop. It may surprise you to find most tunes are the same I IV V or II V I progression in various keys... Of course, blindly creating something from such patterns is a not very fulfilling, but adding your own variations and color can be. Or, deviating from convention for effect becomes viable when you deeply understand those conventions.