So, you see it as a transformation "in a twinkling of an eye". Instantaneously.
What's the point of working toward that point if everyone will be changed in an instant?
Our trial for eternal life is now, before our resurrection. For non-Christians it will be after their resurrection. We have been begotten again as new creatures in Christ, but we are not born again until our resurrection, when we will be changed to have the same divine spirit nature that Jesus currently has. Until then, as a new creature we continue to live in our imperfect human bodies, which prevents us from being 100% perfect. But we can have 100% perfect intentions and will. As Paul said, Romans 7:19-25 (WEB):
(19) For the good which I desire, I don’t do; but the evil which I don’t desire, that I practice.
(20) But if what I don’t desire, that I do, it is no more I that do it, but sin which dwells in me.
(21) I find then the law, that, to me, while I desire to do good, evil is present.
(22) For I delight in God’s law after the inward man,
(23) but I see a different law in my members, warring against the law of my mind, and bringing me into captivity under the law of sin which is in my members.
(24) What a wretched man I am! Who will deliver me out of the body of this death?
(25) I thank God through Jesus Christ, our Lord! So then with the mind, I myself serve God’s law, but with the flesh, the sin’s law.
We are to overcome the temptations of the world, our sinful flesh and Satan. Our resurrection will change us so that we no longer will have the sinful human body, which we currently have to war against, but God will give us a perfect spirit body, uninfected by sin, and so we will be perfect, God having worked in us to make us holy:
1 Thessalonians 4:3 (WEB):
(3) For this is the will of God: your sanctification, ...
Philippians 1:6 (WEB):
(6) being confident of this very thing, that he who began a good work in you will complete it until the day of Jesus Christ.
Philippians 2:13 (WEB):
(13) For it is God who works in you both to will and to work, for his good pleasure.
2 Corinthians 5:17 (WEB):
(17) Therefore if anyone is in Christ, he is a new creation. The old things have passed away. Behold, all things have become new.
Coossians 3:10-17 (WEB):
(10) and have put on the new man, who is being renewed in knowledge after the image of his Creator,
(11) where there can’t be Greek and Jew, circumcision and uncircumcision, barbarian, Scythian, bondservant, freeman; but Christ is all, and in all.
(12) Put on therefore, as God’s chosen ones, holy and beloved, a heart of compassion, kindness, lowliness, humility, and perseverance;
(13) bearing with one another, and forgiving each other, if any man has a complaint against any; even as Christ forgave you, so you also do.
(14) Above all these things, walk in love, which is the bond of perfection.
(15) And let the peace of God rule in your hearts, to which also you were called in one body; and be thankful.
(16) Let the word of Christ dwell in you richly; in all wisdom teaching and admonishing one another with psalms, hymns, and spiritual songs, singing with grace in your heart to the Lord.
(17) Whatever you do, in word or in deed, do all in the name of the Lord Jesus, giving thanks to God the Father, through him.
1 Thessalonians 2:13 (WEB):
(13) For this cause we also thank God without ceasing, that, when you received from us the word of the message of God, you accepted it not as the word of men, but, as it is in truth, the word of God, which also works in you who believe.
1 John 5:4-5 (ASV):
(4) For whatsoever is begotten of God overcometh the world: and this is the victory that hath overcome the world, even our faith.
(5) And who is he that overcometh the world, but he that believeth that Jesus is the Son of God?