Christ imputed righteousness, is his righteousness credited to a sinner who repent and put his faith in Christ.
God demands righteousness, His law that is the transcription of his agape love demands righteousness, but a sinner could not present. Not even from obeying the law. Only through Christ, when he truly repent from his sins and asked for forgiveness, he is forgiven, and Christ imputed righteousness credited to him. He is a sinner justified by faith, having Christ imputed righteousness but none of himself, he was a sinner just then, right?
But this is not for a life time condition. God and His law demands righteousness, and it is Jesus mission to safe people from their sin, and not in their sin.
Every man must stand in their own righteousness before God, to be qualified for heaven.
If those who only has Christ imputed righteousness are qualified for heaven, what would happen?
This man hasn't been changed yet, his character hasn't been perfected, if he had been changed and perfected, he will no longer has the imputed righteousness of Christ, for he is perfect, righteous and sinless.
But if some one believe that it is the only righteousness (Christ imputed righteousness) to qualify him to heaven, he remain in an excuse, that he could never attain sinless perfection in this side of this world, thus, saying he will remain a sinner, he will remain in a imperfect character, in unrighteous heart. How could he be given the permit to live in heaven?
The sin is not blotted out in him will flourish in heaven, his imperfect and unrighteous character will develop in heaven. And heaven will become the same as this old world.
Therefore, there is a clear separation set up by Christ himself:
for the time is at hand. 11 He who is unjust, let him be unjust still; he who is filthy, let him be filthy still; he who is righteous, let him be righteous[e] still; he who is holy, let him be holy still. Rev. 22:11.
The unjust, the filthy will remain in their condition from that time on when the announcement take place, and the righteous, the holy will remain in their righteousness and holiness.
No longer Christ will intersect as a mediator, men has been left to his fate.
And who will be qualified for heaven afterwards? The righteous and holly people.
Who will remain on earth to be burn in hell? The unjust and filthy people.
Where those who rely on Christ imputed righteousness belongs?
Since they believe they couldn't achieve righteousness and holiness in this side of this world, admitting they will remain in their unjust and imperfect character, depending on Christ imputed righteousness, they will be found wanting, and lined themselves with the unjust and filthy people on earth.