"to whom has the arm of the LORD been revealed?" - Isaiah 53:1
On the judgment day, God would be justified if he adds the words "by you" before the '?' I once heard a preacher rightly say that the Church is notorious for being slow. There are probably tens of thousands of humans dying every day and about 80-90% of them are being consigned to hell because they have died as sinners. Even if no one ever preached the Gospel to them, they are accountable before God (as per Romans 1:20), because if they were really sincere about seeking God and wanting to know Him - their Creator - they could have called out to Him in the privacy of their bedroom or slum or forest/cave and God would have definitely revealed Himself to them.
But that notwithstanding, we believers in Jesus have been commissioned by God by default, to preach the Gospel...to evangelize. 'By default' here means that since we have believed in Jesus as the Saviour and repented of our sins, we are automatically supposed to fulfill the Great Commision (or G.C., if you will!), even though the G.C. was given 2,000 years ago.
I work in an NGO where we are developing a surgical simulator to train ophthalmologists to perform cataract surgeries using a low cost technique. Someone in my office once said: