The Book of Mormon preaches in black and white terms. It describes the ideal, and its opposite. Therefore, the idea is that “if ye had all the scriptures which give an account of all the marvelous works of Christ, ye would, according to the words of Christ, know that these things must surely come.”
Verses 34 and 35 describe the state of those who do not believe. These are not simply unbelievers, but those who had the opportunity to know, and repent, but do not do so, even up to the last day. For those, life on earth will have been wasted, for they never achieved the purpose for which they were born.