There are few school of thoughts. One say that enlightenment might be achieved through joy and another one says-suffering. I’m unfamiliar with both, but historically - Buddha and Christ came to help those who suffer. We all suffer same sufferings. Krishna came when Arjuna faced a tough decision. I guess the joy comes only to those who TRULY believe, and the faith raise them above all the suffering and compassion, etc. Have you seen joy in scriptures?
The entirety of the sutras is designed as a system to reduce human suffering. I don’t think belief is a requirement. Follow the steps and you will have less suffering, or so it is contended by Patanjali.