From a purely technical point of view, Chen Fan was not much different from Lei Qianjue.
Lei Qianjue had perfected both his physique condition and usage of Internal Force. He had reached the peak of the Transcendent State and had started to grasp the power of Heaven and Earth. Therefore, he was not any less powerful than an Immortal cultivator at Ethereal Enlightenment level.
What he lacked compared to real Immortal cultivators were Dharma Spells and Divine powers. Without the aid of Chen Fan's divine powers, the match might have lasted much longer than it did.