Let God be true, though every man be a liar. In addition to that, the LDS church regarded this as a prophecy that Christ would indeed return in 1890 or 1891. It did not happen, nor has it happened since. The members of the rising generation died without seeing Christ come. Thus Joseph Smith's prophecy is proven false.
Several problems arise.
All of the apostles, and many more witnesses both before and after them, died being punished by governments of the lands they went into and witnessed to, because they chose to obey God rather than man. This doctrine is not practiced by the vast majority of Mormons living today, except for those in a few Mormon fundamentalist groups. Then Joseph Smith's second prophecy is proven to be false. This prophecy was written July 12, 1843. Less than a year later, he was dead.