The problem is so severe that they have coined a word for it, muboku (無牧), "no pastor." If a missionary is planting a church, it is almost impossible to bring in a pastor from a Bible college. The national pastor must grow up in the church. Older Japanese churches are even in worse trouble.
I blame liberalism and other isms that make the physical more important than the spiritual. Direct evangelism is waning & the social gospellers are in charge. A young pastor near us, a grad of the Japan Baptist Convention seminary, preached that there is no Hell.
Though I did not know him personally, I knew the son and nephew of a missionary who got to Japan as a World War II soldier. Army Captain Eugene Reagan served in Yokohama, Japan right after World War II. His missionary ministry began by teaching Bible classes to Americans. (I think he was already an ordained preacher at that time.) Some of the Japanese people were also interested in the classes. Reagan enlisted a young Japanese man who was not a Christian to serve as his translator. That young man, Sheigeo Kanoya, was converted and became one of the charter members of a Baptist Church that was organized. He was later called to preach and pastored that church for over 50 years. After finishing his service in the army, Brother Reagan went back to Japan as a missionary.