"For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened by the Spirit." (1 Peter 3:18)
Humanity must be resurrected. This is not an incidental "religious" issue: "But if there be no resurrection of the dead, then is Christ not risen" (1 Corinthians 15:13).
Resurrection is required for the believer to enter into eternity (1 Corinthians 15:50) and the non-believer to know punishment in hell.
There are different kinds of "flesh" and other "living" creatures that do not take part in the resurrection, all of which are specifically separated from the "celestial" creation like stars and angels (1 Corinthians 15:39-40).
The earthy image of flesh and blood cannot inherit the kingdom of God (1 Corinthians 15:50). God requires a change from the physical to the spiritual; from the temporal to the eternal. Physical death is an intrusion into the perfect order of the original creation (Genesis 3:19) and a great enemy that will be destroyed (1 Corinthians 15:26).
Resurrection is necessary to correct this awful distortion of the "very good" that God created and is the absolute opposite of physical death. Corruption must become goodness. Dishonor must become glory. Weakness must become power. And the natural must become spiritual.
Jesus Christ made that change possible, proven by His resurrection from the grave (Acts 17:31). The gospel insists on the birth from above (John 3:3) that makes a transfer from death to life (John 5:24)--the new creation (2 Corinthians 5:17) that will ultimately consummate in "all things" being made new (Revelation 21:5).
We await the fulfillment of that promise when we will be freed from the curse of death. HMM III