I take that literally. No one, but no one, will come to the Father and end up in heaven except through the eternal Son of God. Who else could resurrect us to the perfect love of heaven?
That means that no one in the time before the incarnation of the Son of God, and no one, but no one, after His coming into our world will end up heaven except through Him. To take that literally I include all babies who die in infancy, all retarded people, and all people in the OT period and NT period and ever since of any nation whatsoever.
The text clearly says "but by me." No one will be in heaven except through Christ, but for two thousand years Christian tradition has presumed to add its ideas of what humans have to do to make it. For the first fifteen hundred years till the Reformation Christian tradition added that you have to be baptized to be saved through Christ. Till very recently Roman Catholic theology held that unbaptized babies could not be saved - they weakened that tradition by inventing the idea of limbo which wasn't quite hell, but bad enough.
For the past five hundred years Protestants have said that it is not baptism that saves you, which is correct. But then we added the tradition that you must get to hear about Christ and make the right informed decision about Him to be saved. We weakened that by saying that Abraham was saved by looking forward with a proper faith to the death of Christ. As for babies who couldn't look forward, most Protestants said without a shred of Scripture to back it that babies were saved because they hadn't attained the age of reason.
If I am right the whole of Christian tradition, with some exceptions, has been wrong in adding to the words of Jesus. No one will be in heaven except through the Messiah, but He never said we had to understand HOW he saves us.
How He does it is probably far more costly and wonderful than anything we have any idea of. But it seems to me monstrous to believe the tradition that baptism or the opportunity to hear, or some decision, or cerebral understanding of the way of salvation is what saves us. That does more to make it hard for reasonably moral persons to believe the Bible than any words of Jesus.
In that sense I would rather go by the Bible alone than two thousand years of Christian tradition. The Reformation was right about "sola scriptura" which means we neither add to nor take away from the Bible, especially the words of Jesus. The Reformation was also right about "by grace alone" which means that there is nothing humans have to add to the saving grace of Christ.
It was C.S.Lewis who brought us back into grace alone by assuring us
that no one will be sent to hell who could possibly be happy in heaven
(The Great Divorce based on John 3:17-21). That honours the Son
of God as a far more wonderful Saviour than we imagined. Tradition has
painted Him as a monster.