Here's my proposed answer,
@bbbbbbb.
First, we need to see that Jesus came to save us from death, not second death.
Second, we need to recognize that He
has saved us from death...all of us. But the salvation isn't realized yet, nor will it be until He returns. That's when the salvation happens, when the dead are raised. Who will be resurrected? Everyone, some to eternal life and some to eternal condemnation.
He told us all blasphemies against Him will be forgiven, but blasphemies against the Holy Spirit will not be forgiven. I think that means that even those that never knew Christ will be forgiven and raised to new life; and then comes judgment. Rev 20:12 says, "and the dead were judged out of those things which were written in the books, according to their works."
But it doesn't say they were sentenced according to their works. Rather, it says they were sentenced based on whether their names were in the book of life, which we all recognize as believing in Jesus Christ, right? But if they lived before Christ, especially if they were Gentiles, they wouldn't know to believe in Christ. God, being just, wouldn't punish them forever for not having heard tge gospel. So why not at that particular time? Wouldn't that be the perfect time to tell them the gospel, and if they believe, or if they bow the knee to Christ, He writes their name in the book of life right then.
And I don't see why He wouldn't treat those born after Christ that haven't heard the gospel in exactly the same way.
If they did hear the gospel and rejected it, they fall into the category of those who blaspheme the Holy Spirit, because they didn't follow His promptings. They are cast into the lake of fire.