Believers must share the Gospel far and wide, yes.

But it is not Christians who create new believers, but God who regenerates unbelievers and draws them into Christ forever.

TLDR: you are being dutiful to share the gospel, but you are not converting people yourself.

The gift of salvation is available to all believers, but only those whom God regenerates can have true belief.

In other words, Christ died for God's elect people, not the world.