Part of the point is that the competitor chooses the routine based on what they can get the most points for. They are marked not only on quality of execution,

Part of the point is that the competitor chooses the routine based on what they can get the most points for. They are marked not only on quality of execution, but technical difficulty of the routine. Crudely speaking, what this means is that a competitor aims to perform the most difficult routine that they can do perfectly. This is not dissimilar to weightlifting.