Nephi has been pondering for over four decades about the great revelations given to him in the Arabian Peninsula. (2 Nephi 4: 16 and 2 Nephi 5: 34.) His creation of, and inscription on the plates were after these long deliberations and reflections.
When he says "the things which I have written sufficeth me," he is putting a punctuation mark on his plates. He is saying he has finished his ministry, finished his prophecy. He has refined and set out his message in a deliberate, careful way. These books of Nephi are not internet blogs undertaken daily. They are not rapid-fire responses, nor stream-of-consciousness statements. They were planned for the ages. Born from pondering, inspired by revelation, described as prophecy by the author, and filled with light and truth if considered with care by any reader. Nephi's pronouncement that they "sufficeth me" is a powerful statement by an aging prophet.
Years of preparation and reflection allow him to "speak plainly" to us. There's no need to be vague. No reason to hide our plight from us. He wants us to understand. When he attempts to "speak unto you plainly, according to the plainness of my prophesying," we read into it the wrong definitions, associate his words with others who will never read the book, and consider ourselves blessed and vindicated instead of condemned, and called to repentance. We do that a lot. What good is it to read things which tell you to be proud? Why follow a religion that tells you you've no reason to repent? Everyone but you is going to hell, right? (Alma 31: 17-18.) Because so long as you remain affiliated with the broad mainstream of your church, God will save you. And if there's any hint of error, He will beat you with a few stripes and all will be well. Nephi has already condemned that as an error, hasn't he? (2 Nephi 28: 8.)
If his words were plain and intended to be taken at face value, why read into them justification for yourself and your sins? Why think they condemn everyone but you? Why are they speaking in disparaging terms about those who will never have the book? Why did Nephi write a book condemning only those who will never read it? Surely, if he was in fact "plain" in his meaning, then we ought not read anything into it other than what it says and how it says it. It must be a message to us.
If it is addressed to us, then we have more than one "wo" pronounced upon us by Nephi. We have been warned. We need to change what we are doing. The gentiles with whom we are identified (D&C 109: 60) are collectively condemned. We need to separate ourselves by our behavior from theirs. We need to repent.
Now, just in case you think, as a recent comment has asserted, that the Lord has sent another message vindicating us as a collective gentile body/church in D&C 1: 30, I would remind you that revelation came from the Lord in 1831. In the following year the Lord gave another revelation that put the church under condemnation. (D&C 84: 54-58.) We know that condemnation was not lifted, because of President Benson and Elder Oaks.
More troubling still is the Lord's threat to reject the gentile church altogether in January of 1841 if the church did not follow His strict appointment and complete building a temple in the time He provided. (D&C 124: 31-32.) The warning was given that even if the temple were built, we would still be condemned if we failed to do what He said. (D&C 124: 47-48.)
Did we keep the appointment given us? The Nauvoo Temple was not completed before Joseph Smith died. The endowment was not completed by Joseph, but Brigham Young was told he had to finish it. (See this post dated June 30 titled 1 Nephi 13: 33-34.) Did we keep the appointment? Have we been able to avoid being rejected as a church? Have our covenants been fulfilled?
Why do we repeat endlessly the praise from 1831 but ignore the threatened rejection that came in 1841? From January of 1841, until Joseph's death in June of 1844, we had three and a half years to complete the Nauvoo Temple. Was that "sufficient time" to do what was required of us? If so, we did not complete it. Why was Joseph taken? Was that any indication about when the "sufficient time" expired? If so, what then? Where would that leave us?
Is our best hope to be found in the messages and warnings of the Book of Mormon? Can there be gentiles found who will believe its message? How carefully ought we study it?
Did you know the church had almost no use for the Book of Mormon until Hugh Nibley's efforts? (You know that if you've read Eighteen Verses.) Hugh Nibley, by his efforts beginning in the 1950's, practically discovered the Book of Mormon for the church. He's gone now.
Even though Moses was taken from ancient Israel, and with him the authority of the priesthood, (see D&C 84: 25-26) the ancient Israelites remained the Lord's people. He still worked through them and sent them messengers from time to time. These messengers were rarely the High Priest. Although in Samuel's case he displaced the High Priest. (1 Samuel 3: 1-21.) They were sent from time to time. Their qualifications were private, as the Lord told Moses they would be. (Numbers 12: 6.) I have no doubt Hugh Nibley was sent to us. If you've paid close attention, his departure has created an intellectual collapse at the center of the faith, with various egos contending to be noticed. They aspire to put upon them Hugh Nibley's mantle. They are not made of the same stuff, called with the same calling, nor endowed with the same capacities.
I doubt we'll see someone like him again. Perhaps we may someday see someone with an equally important message, but among those born in this dispensation, there is none to compare to Brother Nibley.
Well, now we're off-point again. So back to Nephi...