Some are making the assumption that because they haven’t heard about missionaries sent to these isolated peoples, those cultures don’t know how to be saved and will be sent to hell.
Read “Eternity in their Hearts” by Don Richardson, where he describes missionaries who HAVE gone to these cultures, only to learn that they DO know about a God trying to save them.
Or, reports about Muslim converts to Christianity show that about 1/3 have done so because Jesus appeared to them in a vision or dream.
“Eternity in Their Hearts” is an AWESOME book.