Nephi includes very succinct summaries of each of these passages in verses 9 and 11:
Isaiah 2-5 (from verse 9): "And as one generation hath been destroyed among the Jews because of iniquity, even so have they been destroyed from generation to generation according to their iniquities;"
Isaiah 6-12 (from verse 9): "...never hath any of them been destroyed save it were foretold them by the prophets of the Lord.
Isaiah 13-14 (from verse 11): "And notwithstanding they have been carried away they shall return again, and possess the land of Jerusalem; wherefore, they shall be restored again to the land of their inheritance."
Iniquity leads to destruction. Prophets warn the people. A remnant shall return.
If you had to summarize Isaiah 2-12 in 12 words, this is how I would do it. Perhaps Nephi loved Isaiah so much because his message was so similar to what Nephi was experiencing. He was called as a prophet as the Lord created a remnant out of his father's seed, but he saw in vision that his seed would ultimately ripen in iniquity and reject the warnings of the prophets, leading to their utter destruction. And yet, in the latter days, a remnant will return.