1 Corinthians 15:40-46 (ESV) reveals the mystery of the natural and heavenly/spiritual bodies, and that human beings will be granted the latter at the resurrection:
40 There are heavenly bodies and earthly bodies, but the glory of the heavenly is of one kind, and the glory of the earthly is of another. 41 There is one glory of the sun, and another glory of the moon, and another glory of the stars; for star differs from star in glory.
42 So is it with the resurrection of the dead. What is sown is perishable; what is raised is imperishable. 43 It is sown in dishonor; it is raised in glory. It is sown in weakness; it is raised in power. 44 It is sown a natural body; it is raised a spiritual body. If there is a natural body, there is also a spiritual body.
45 Thus it is written, “The first man Adam became a living being”; the last Adam became a life-giving spirit. 46 But it is not the spiritual that is first but the natural, and then the spiritual.
Matthew 22:30 (ESV) sheds more light on this, revealing that this is the same nature of the angelic beings:
30 For in the resurrection they neither marry nor are given in marriage, but are like angels in heaven.
However, when God created man with a natural/earthly body, He claimed that it was very good (i.e. perfect):
31 And God saw everything that he had made, and behold, it was very good. And there was evening and there was morning, the sixth day. [Genesis 1:31 ESV]
If everything was made perfect in the beginning, then why do human beings need to change their earthly bodies into spiritual/heavenly/angelic bodies? Why weren't human beings created with spiritual/angelic bodies from the very beginning?