When Nephi was quoting from Isaiah 29, he quoted verse 8 which spoke of a hungry man who was dreaming, and only ate in his dream. In the time when the Book of Mormon is to come forth, there will be churches—but for Nephi they will be like the dreaming man. They will not have the substance.
Nephi is probably also alluding to another verse that he had quoted as part of the long section of Isaiah chapters. In Isaiah 5:21, Isaiah declares: “Woe unto them that are wise in their own eyes, and prudent in their own sight!” The competing churches are placed into that category. Nephi says, in verse 4, that “they shall teach with their learning.”
These statements are also probably part of fulfilled prophecy, for Joseph Smith would have heard many of these arguments as he attended different churches. Each would proclaim its own truth, one of which was that the age of miracles ended with the New Testament. Nephi predicts people saying one to another: “this day he is not a God of miracles; he hath done his work.”