Is the gospel already preached to all nations and people?

Mosiah 15:28

28 And now I say unto you that the time shall come that the salvation of the Lord shall be declared to every nation, kindred, tongue, and people.

Already, the gospel has spread to all continents and most people. Of course, this is not the case for tribes who still do not have access to language and modern culture.

So, what happens to China, North Korea, and uncivilized tribes who have yet to officially access the gospel, even though it is written in the scriptures?

I don't think this scripture has been fulfilled yet. To achieve this scripture, many missionaries and leaders constantly study, work hard, and pray for countries and people who will someday have a chance to accept the gospel.

It is the present progressive, and we're part of the wheel that rolls around - dispensation to achieve that feat.