In the following Scripture, the apostle Paul wrote on the Millennial Kingdom that will begin after Christ’s return to earth and end when he has defeated all of his enemies, including death. It establishes that even after Jesus returns to reign, there will still be sinners and death in the world, just as the prophets foresaw.
“No more shall there be in it an infant who lives but a few days, or an old man who does not fill out his days, for the young man shall die a hundred years old, and the sinner a hundred years old shall be accursed.” Isaiah 65:20
If the kingdom was to only manifest itself in a world free of unbelievers, then Israel could never fulfill her destiny as a light to the nations, showing them the way to the LORD.
”For as in Adam all die, so also in Christ shall all be made alive. But each in his own order: Christ the first fruits, then at his coming those who belong to Christ. Then comes the end, when he delivers the kingdom to God the Father after destroying every rule and every authority and power. For he must reign until he has put all his enemies under his feet. The last enemy to be destroyed is death.” 1 Corinthians 15:22-26
Jesus must reign until He has put all of His enemies under His feet. When the Kingdom of God is handed over to the Father it will be free of sin and death, identifying it as the Eternal State (Revelation 21:4, 8). This Scripture is a basic summary of future events, supporting the plain reading of Revelation 20.
”Then I saw thrones, and seated on them were those to whom the authority to judge was committed. Also, I saw the souls of those who had been beheaded for the testimony of Jesus and for the word of God, and those who had not worshiped the beast or its image and had not received its mark on their foreheads or their hands. They came to life and reigned with Christ for a thousand years. The rest of the dead did not come to life until the thousand years were ended. This is the first resurrection. Blessed and holy is the one who shares in the first resurrection! Over such the second death has no power, but they will be priests of God and of Christ, and they will reign with him for a thousand years.” Revelation 20:4-6
There is simply no way that you can read this passage and deny that Jesus reigns with the resurrected Saints for one thousand years on this planet and the Adamic curse is still in effect. We are not in the eternal state with a new heaven and new earth until after the second resurrection and the White Throne judgement.
”Then I saw a new heaven and a new earth, for the first heaven and the first earth had passed away, and the sea was no more. And I saw the holy city, new Jerusalem, coming down out of heaven from God, prepared as a bride adorned for her husband. And I heard a loud voice from the throne saying, “Behold, the dwelling place of God is with man. He will dwell with them, and they will be his people, and God himself will be with them as their God. He will wipe away every tear from their eyes, and death shall be no more, neither shall there be mourning, nor crying, nor pain anymore, for the former things have passed away.” Revelation 21:1-4