The gap between immortals and mortals is like a chasm, not something achievable solely through sheer will. The immortal Eternity is not yet a true immortal and is currently in the Transcendance Tribulation Stage.
Although he lacks a physical body and only possesses a soul, he's not a typical Transcendance Tribulation Stage practitioner. However, with the immature Eternity Dao Fruit he possesses, he compensates for his lack of combat power.
If one in the Transcendance Tribulation Stage encounters Immortal Eternity in the spiritual space, they would be at a disadvantage.
Yet, Immortal Eternity has met with the true Fairy Eternity.
The power of the immature Dao Fruit couldn't manifest before the true Dao Fruit.
After being taught a lesson, Immortal Eternity comprehends that he may not be a true immortal, but rather an imitation of Fairy Eternity.
"As for the origin of the Dao Fruit, elder, what's your thought?", Yun Zhi posed this question to Fairy Eternity.