What is the solution for a supervisor's procrastination in setting a thesis defense date, despite the completion of all necessary requirements?

You have not specified the reason that prevents the professor from presenting your thesis for discussion. However, if you believe he is academically deficient or failing in his responsibility, there is no harm in informing his superiors to rectify his conduct or to request another supervisor in his stead. This notification should only occur after despairing of the effectiveness of other methods.