One of the hallmarks of the 'Christian universalist' presentation is that he determines that when Scripture speaks of "all creation" being reconciled it must invariable mean every person and created being without distinction.
When it comes to the Bible, "all" does not mean "all." In other words, 'all creation' can speak of an expansive concept through out creation, all in terms of vastness, not necessarily all in terms of comprehensive of each individual and being. For example, are notoriously divided over whether or not Satan and demons are reconciled (set aside that Scripture says they are not and Christ did not die for angels).
Consider Colossians 1:20
Colossians 1:20 and through him to reconcile to himself all things, whether on earth or in heaven, making peace by the blood of his cross.
Read the context. In Colossians 1:22-23 it is clear that only those who believe and remain in the faith are those who will be reconciled and presented blameless in the day of the Lord.
Colossians 1:22 he has now reconciled in his body of flesh by his death, in order to present you holy and blameless and above reproach before him, 23 if indeed you continue in the faith, stable and steadfast, not shifting from the hope of the gospel that you heard, which has been proclaimed in all creation under heaven, and of which I, Paul, became a minister.
The Christian universalist then plays fancy with Christ's judgment and the Day of the Lord. It might not be final--and so of course everybody is saved only through faith in Christ--and they might come to faith after the day where those who believed in this life are present spotless and holy.* To which we reply like Paul "μὴ γένοιτο" ("May it never be" or "God forbid") and which we reply this way not because it is not a nice idea--for on the surface it seems more pleasurable-- rather it runs contrary to the Biblical concept of the Last Judgment. And it's called the Last Judgment for just that reason.
Consider a more potent example:
The New Heavens and the New Earth is the final state of the resurrection of the righteous. It is the restoration of ‘all creation’ yet we should understand that the unrighteous are made to dwell in away from God’s goodness and under his wrath that has been kindled for them:
Isaiah 66:22 “For as the new heavens and the new earth that I make shall remain before me, says the Lord, so shall your offspring and your name remain. 23 From new moon to new moon, and from Sabbath to Sabbath, all flesh shall come to worship before me, declares the Lord. 24 “And they shall go out and look on the dead bodies of the men who have rebelled against me. For their worm shall not die, their fire shall not be quenched, and they shall be an abhorrence to all flesh.”
Notice that contrary to the universalist “all flesh” does not mean every individual but “all flesh” living in the time of the New Heavens and New Earth who have experienced eternal life. There is a clear distinction between "all flesh" those who are "of your offspring and your name" (and perhaps other created beings) vs. the dead bodies of men who rebelled and are 'cut off from the land of the living.'
The New Heavens and the New Earth is the final state of the righteous and it lasts forever. They enjoy everlasting life and are classified as part of "all flesh." Those under the second death are not part of the "all flesh" but are under death and God's eternal judgment.
The final state of the wicked lasts equally long as the state of the righteous. Again we are told the fire is not quenched. The worm that eats at them does not die mean it does not end. In this life when a worm eats a dead corpse it will run out of food to consume and die--not so in the final state.
In this day, the wicked will not switch teams. They will not turn and worship rather they shall be looked upon for their rebellion. They have rebelled and their is no turning back.
Of course, as Paul says "now is the Day of Salvation"--by all means please turn and be saved.
*See for example Gregory MacDonald The Evangelical Universalist, pp. 43-48.