We cannot reach an unbelieving world. But Christ can. He has the authority. He paid the price for sin. His love calls people to Him. He can reach an unbelieving world.
But He does desire to use His people in doing this. His command to us is to go. That doesn't necessarily mean that we have to pack our suitcases and take off for some far away place. Some He calls to do that, but all of us are told to preach the Gospel wherever we go. That means where I am now as well as where I might be next week.
We are told to go and preach, not our own ideas, but His Gospel. It is His authoritative message of love and deliverance through Him that is to be our one message.
We are told to go and preach to every one. We are not told to shy away from sharing the Gospel with those who reject it, or scorn it. Everyone we meet is someone who needs to hear the Gospel from our lips.
We are told to go and preach to every one because Jesus is always with us. He has not sent us out on an impossible mission alone. If He had, the mission really would be impossible to complete. But He has sent us in His authority and in His power to proclaim His truth. And He is with us every step of the way.
We were never told to save anyone, to convince anyone, to secure anyone, to convert anyone. That is His perogative. We are to go and tell in His power and authority and love.
"If the world hates you, keep in mind that it hated me first. If you belonged to the world, it would love you as its own. As it is, you do not belong to the world. That is why the world hates you." (John 15:18)
The rejection of the authority of the Scriptures today really is not anything new. People did that in Jesus' day as well. And the world tends to hold those who speak of this authority in contempt. It is because we are not part of the world that the world hates us. But the world hated Jesus first. Hatred for Him does spill over onto His followers.