Your conclusion about what this verse means is based on your bias, not on what it actually says. It doesn't say that we were unregenerate when we believed. The same author John says in 1 John 5:1 "everyone who believes that Jesus is the Christ is born of God..." He says "who believes... is born." It means that if I believe, I'm already born of God. It doesn't say "will be" or "can be" as you purport. It says "is," which means that the moment I believe, I
am born of God. Whether one speculates that it is simultaneous or not, according to Paul's writings in 1 Cor. 2:14 and elsewhere, spiritual birth logically precedes faith. The one not spiritual can't understand, because the gospel is spiritual in nature. The one who understands and believes is already spiritual.
So then, when Jesus said the Spirit will convict the world, by systematic study of the scripture and observation of what actually happens, this is what it has to mean:
1. "the world" = not just Jews, but all nations
2. "He will convict" = The Spirit moves on people to make them spiritual people by spiritual rebirth, giving them the spiritual wisdom that only comes from above.
Reference John 3:8 "The wind blows wherever it pleases. You hear its sound, but you cannot tell where it comes from or where it is going. So it is with everyone born of the Spirit." "You can't tell" means that human reasoning can't come to the correct conclusion about the gospel, because it is spiritual in nature. It takes an act of God to make someone born of Him. It's not a human decision (Jn. 1:13).
So according to Paul in 1 Cor. 2:14, a person has to be born again (be a spiritual person) in order to understand and believe the gospel.
TD