Not all applications are progressed beyond the initial application.
The RAF are looking for a balance of academics/work experience/volunteering/extra-curriculars/fitness/hobbies.
Essentially, the more active, motivated, resililient, and determined to succeed you are, the more likely you are to progress.
The application process can be very lengthy, requiring patience and flexibility.
Call your local careers office for advice on your application, they will be more than happy to help.