What I understood him to say was that Christ's life was insufficient to convince the universe that man can obey God's law, that the 144k is the final "proof" that man can keep God's law. Without the perfection of the 144k, the whole human race would be lost, including the faithful ones of old.
If Jesus settled everything, if He disproved all of Satan’s lies and accusations, why, then, are we still here? Why aren’t we in heaven? Why isn’t Satan and sinners dead and gone? Why is God allowing the great controversy to continue?
If Jesus won the great controversy on the cross, or at His resurrection, why, then, is it still going on? What more must be proven in order for God to win great controversy, to destroy sin and sinners in the lake of fire, to restore paradise?
Sister White explains why the great controversy did not end at the cross. She gives two reasons: 1) Holy angels did not understand all that was involved in the great controversy, and 2) Satan changed tactics, his strategy.
Yet Satan was not then destroyed. The angels did not even then understand all that was involved in the great controversy. The principles at stake were to be more fully revealed. And for the sake of man, Satan's existence must be continued. Man as well as angels must see the contrast between the Prince of light and the prince of darkness. He must choose whom he will serve. {DA 761.3}
By His life and His death, Christ proved that God's justice did not destroy His mercy, but that sin could be forgiven, and that the law is righteous, and can be perfectly obeyed. Satan's charges were refuted. God had given man unmistakable evidence of His love. {DA 762.4}
Another deception was now to be brought forward. Satan declared that mercy destroyed justice, that the death of Christ abrogated the Father's law. Had it been possible for the law to be changed or abrogated, then Christ need not have died. But to abrogate the law would be to immortalize transgression, and place the world under Satan's control. It was because the law was changeless, because man could be saved only through obedience to its precepts, that Jesus was lifted up on the cross. Yet the very means by which Christ established the law Satan represented as destroying it. Here will come the last conflict of the great controversy between Christ and Satan. {DA 762.5}
That the law which was spoken by God's own voice is faulty, that some specification has been set aside, is the claim which Satan now puts forward. It is the last great deception that he will bring upon the world. He needs not to assail the whole law; if he can lead men to disregard one precept, his purpose is gained. For "whosoever shall keep the whole law, and yet offend in one point, he is guilty of all." James 2:10. By consenting to break one precept, men are brought under Satan's power. By substituting human law for God's law, Satan will seek to control the world. This work is foretold in prophecy. Of the great apostate power which is the representative of Satan, it is declared, "He shall speak great words against the Most High, and shall wear out the saints of the Most High, and think to change times and laws: and they shall be given into his hand." Dan. 7:25. {DA 763.1}
Men will surely set up their laws to counterwork the laws of God. They will seek to compel the consciences of others, and in their zeal to enforce these laws they will oppress their fellow men. {DA 763.2}
The warfare against God's law, which was begun in heaven, will be continued until the end of time. Every man will be tested. Obedience or disobedience is the question to be decided by the whole world. All will be called to choose between the law of God and the laws of men. Here the dividing line will be drawn. There will be but two classes. Every character will be fully developed; and all will show whether they have chosen the side of loyalty or that of rebellion. {DA 763.3}
Then the end will come. God will vindicate His law and deliver His people. Satan and all who have joined him in rebellion will be cut off. Sin and sinners will perish, root and branch, (Mal. 4:1),--Satan the root, and his followers the branches. The word will be fulfilled to the prince of evil, "Because thou hast set thine heart as the heart of God; . . . I will destroy thee, O covering cherub, from the midst of the stones of fire. . . . Thou shalt be a terror, and never shalt thou be any more." Then "the wicked shall not be: yea, thou shalt diligently consider his place, and it shall not be;" "they shall be as though they had not been." Ezek. 28:6-19; Ps. 37:10; Obadiah 16. {DA 763.4}
Personally, I do not subscribe to the final generation theology as it is normally presented. I believe character perfection has been available to everyone since the beginning of the great controversy. The difference between the resurrection generation (the great multitude) and the translation generation (the 144,000) is not character perfection; no, the only real difference has to do with whether or not they are resurrected or translated.
No one is saved based on their “fitness for heaven”. Everyone is saved based on their “title to heaven”. Some resurrected saints are more mature, more seasoned, more developed than some translated saints. In other words, they are more fit for heaven. In fact, people like Paul and John are more mature, more fit than the fittest of translated saints. They would have fared more famously during the final tribulation than did the translated saints.