The Gospel must first be preached to all nations. I think that’s in Matt 24. The only ones left are islamic strongholds and a few obscure languages in jungles.
The Gospel is preached in those nations. Across satellite TV, across bible smugglers and underground churches there, from people who smuggle dvds of ‘The Jesus Film’ to those areas.
You said — “The Gospel must first be preached to all nations.”
It will be during the Tribulation. Revelation tells us about the angel that gives the Gospel to the entire world...