The true gospel message, is going out into every corner of the world. The Lord Jesus said it would be preached everywhere, and then the end will come.
The world doesn't reject the gospel in ignorance, so it's not due to lack of preachers. The world has and is hearing the true gospel being preached, but they wilfully supress the truth in unrighteousness. So they are without excuse. Some may say, "what about those who lived in isolated parts of the world and they never heard the gospel, and died without ever hearing it".
The bible declares that there are no Atheists, everybody knows God exists. Creation itself testifies that God exists, even the ignorant people can't deny it. They look in the mirror and see the evidence right there before them, so they can't deny that God exists.
God will judge those who died without ever hearing the gospel differently to those who heard it many times and rejected it every time.
The bible says something like "to whom much is given, much will be required of them".
The gospel is good news to believers, but it's the worst news that unbelievers will ever hear. This is why some walk out of our Church services, they can't stand hearing the true gospel message, because they realize that the good news is not for them.