It's a gathering of the sealed people of God, which are now only in Christ Jesus. Where there is neither Jew nor Gentile, but only redeemed saints of God.
Col 3:11
Where there is neither Greek nor Jew, circumcision nor uncircumcision, Barbarian, Scythian, bond nor free: but Christ is all, and in all.
NT prophecy cannot contradict NT doctrine of Christ.
If there is Christian Jew not Greek, then there is Christian circumcision and uncircumcision. Segregating Christian Jews from Gentiles, is the schism of commanding circumcision in the body of Christ.
Jas 1:18
Of his own will begat he us with the word of truth, that we should be a kind of firstfruits of his creatures.
1Co 16:15
I beseech you, brethren, (ye know the house of Stephanas, that it is the firstfruits of Achaia, and that they have addicted themselves to the ministry of the saints,)
Firstfruits of both Jews and Greeks born again into the body of Christ.
No one can rightly interpret Rev 14, by changing doctrine of Christ.
The time of the nations ruled by unjust men, will end at the Lord's return. He will resurrect and rapture all His firstfruit harvest from the earth, defeat the armies of the nations, and govern all nations with His resurrected saints.
The time of nations ruling themselves without Christ, will end with Christ ruling all nations without injustice.
Romans 11 is an assurance to believing Jews being grafted in again, and a rebuke to Gentile Christians believing no Jew could believe and be grafted in again...
Rom 11:1
I say then, Hath God cast away his people? God forbid. For I also am an Israelite, of the seed of Abraham, of the tribe of Benjamin…Even so then at this present time also there is a remnant according to the election of grace.
Rom 11:18
Boast not against the branches. But if thou boast, thou bearest not the root, but the root thee. Thou wilt say then, The branches were broken off, that I might be graffed in. Well; because of unbelief they were broken off, and thou standest by faith. Be not highminded, but fear: For if God spared not the natural branches, take heed lest he also spare not thee.
The Jews were first grafted again into the Israel of God, when Mary Magdalene believed Jesus' resurrection and confessed Him Lord. The first record of Gentiles grafted into God's Israel, was the Roman Cornelius and his house.
You believe wrong that every human on the planet receives the mark, which Jesus never says.
Rev 13:8
And all that dwell upon the earth shall worship him, whose names are not written in the book of life of the Lamb slain from the foundation of the world.
All that dwell upon the earth,
whose names are not written in the Lamb's book of life, shall worship him.
The Scripture does not say, All dwelling upon the earth
are names not written in the book of life and shall worship him.