Because not everyone can receive feedback from the cosmic origin.
First is the weight: unless one is at the Demigod Level, it's impossible to receive feedback.
Next is the method: when Zhao Xing previously forced Venerable Zhaibing to death, theoretically speaking, the origin of Venerable Zhaibing should have returned to the universe because of Zhao Xing, but he didn't become stronger through feedback.
In essence, it's because Zhao Xing has not yet cultivated the 'Heaven Repairing Technique'. According to Wei Tianchen, cultivating the Heaven Repairing Technique establishes a connection with the cosmic origin. Only then, when you kill the 'parasite,' will you receive feedback.
Cultivating the Medical Dao can also help Zhao Xing better understand the 'Heavenly Change Divine Needle,' as this Marquis Transformation Divine Artifact itself combines the Dao of the Doctor and the Minister of Agriculture.
