These chapters, and many more to come after this, are quoted verses from Isaiah, the Old Testament prophet. Any who have tried to read Isaiah know how difficult it is to understand him at times. In 2 Nephi 15, which corresponds with Isaish 5, the Prophet speaks of the Lord's vineyard.
Upon gathering building materials, and sowing choice wine grapes, building a wine-press and waiting for the reaping of his labors, the Lord discovers not delicious cultivated grapes, but wild grapes that are good for nothing. Wild grapes aren't as sweet and can actually be quite sour, have a grittier texture, and if treated the same way as domesticated wine grapes when making wine, can cause a burning sensation in the throat. So, they aren't desirable, and they are usually a disappointment when reaped instead of the cultivated grapes that were sown.
When we understand the underlying message Isaiah is trying to tell us, and the Nephite prophet Jacob, we see that the grapes are compared to the children of God. Our Heavenly Father sent us to earth to be tested, and to see if we would follow His commandments, in hope that we would return to His presence. He "sowed" us in his vineyard, and had faith that we would turn out to be domestic grapes, ready to become delicious, desirable wine. Instead, He has found that many are turning out to be sour wild grapes, that aren't able to be turned into the wine He desires. Upon finding these in a real life situation, the Lord of the vineyard would burn the vineyard, and start the process over again in better hopes. Our Heavenly Father gives us repentance though, and through Jesus Christ we can be transformed into good wine grapes.
The Lord is calling those who have sinned, and asking them to come to Him and repent. Those He gathers will be safe from the burning. However, those who do not listen aren't saved from the destruction that must take place in order to create a wine grape yielding garden. How important is it for us to spread the message of repentance to those who aren't listening? How vital for us to save our brothers and sisters before the destruction of the last days come?