Christ gave a parable of a rich man and a beggar. In it, the beggar, named Lazarus, sits at the gate of the rich man's house. He begs for food, and has no company other than the rich man's dogs. After they both die, no mention is made of Lazarus' funeral, but it mentions that the rich man was buried, certainly a grand occasion. However, in the afterlife, it's a much different scenario. Lazarus is in the bosom of Abraham (a common term at the time for paradise as used by the rabbis) and the rich man is in fiery torment. He calls up to Father Abraham, asking to send Lazarus down so he can dip his finger in water, and give the rich man just a drop to satisfy his parched tongue. Abraham says no. Then, the rich man, thinking of his family, his father and brothers, asks Abraham to send Lazarus to them, to warn them of what awaits them if they continue on the path they're on. Abraham responded, saying "If they hear not Moses and the prophets, neither will they be persuaded, though one rose from the dead."
How true is this? Often, people will say "I'd believe if I saw an angel" or something along those lines. I've personally heard that multiple times. But that's not true. We have all the evidence we need: we have the Bible, we have the Book of Mormon, we have a Prophet and Apostles, and the testimony of them, as well as millions of members worldwide. We have enough evidence of the truth, and if people will turn a blind eye to that evidence, and still not believe, and rather go completely against it, then their hearts are so hardened that not even an angle, a resurrected being, or a loved on who has passed coming to them and telling them, in no uncertain terms, of the errors of their ways and what they should do to save themselves will convince them. They're set in their ways, and they aren't about to change, and not even angelic and divine messengers will change that.
We know what's what. It's up to us to take what we have, look into, study it out, and find out for ourselves if it's true. If we choose not to take that advice, or to ignore the answer we get, then it's on us. The truth is out there, and no heavenly vision is going to tell us, God doesn't work like that. It's up to us.