Interestingly, rather than shouting out in rejoicing that all who repent will escape punishment, the angel instead pronounces a "wo" upon the gentiles. It is almost as if the future of the gentile conduct inspires nothing but pessimism for the angel. It inspires another warning and condemnation for the gentiles who, having received the Book of Mormon and other sacred writings, are then fully responsible to repent.
Notice that the relationship is between the "Lamb of God" and the gentiles. It is not between the gentiles and "leaders" or "prophets" or "administrators" or "general authorities" or even messengers. It is between the gentiles and "the Lamb of God."
Why that specific a relationship? Why is it exclusively between the individual and Christ?
Read again the description of the Telestial folk who return "worlds without end" to their condemnation: "And the glory of the telestial is one, even as the glory of the stars is one; for as one star differs from another star in glory, even so differs one from another in glory in the telestial world; For these are they who are of Paul, and of Apollos, and of Cephas. These are they who say they are some of one and some of another—some of Christ and some of John, and some of Moses, and some of Elias, and some of Esaias, and some of Isaiah, and some of Enoch; But received not the gospel, neither the testimony of Jesus, neither the prophets, neither the everlasting covenant." (D&C 76: 98-101.)
From what you've now learned can you see how one might follow even a true messenger but fail to gain "the testimony of Jesus?"
Can you now understand why, although you have followed messengers, you may have not in fact received the "everlasting covenant?"
The Temple is a type and shadow. It is a symbol of the real thing, but it is not the real thing. The "everlasting covenant" is taught there. But to gain it you must receive it through "the testimony of Jesus." Is this "testimony of Jesus" yours? Of is it rather Jesus testifying to you? If it is He testifying to you, then what must His testimony be?
In light of that does it mean then to "harden your hearts against the Lamb of God?" As you answer that, keep in mind His formula in D&C 93: 1: "Verily, thus saith the Lord: It shall come to pass that every soul who forsaketh his sins and cometh unto me, and calleth on my name, and obeyeth my voice, and keepeth my commandments, shall see my face and know that I am." Here Christ is but reiterating the message of the Book of Mormon.
Then how do you repent? I was asked about idolatry among the Saints. Anything that separates you from the Lamb of God is an idol. Cast it aside and come to Him. Why we have idols between us and the Lord is as different as one person is from another. Almost without exception, it comes as a result of a false tradition handed down. Your false traditions are based on your life's experiences while another's false traditions are based on theirs. No matter what they are or how they were acquired, whatever separates Christ from you must be set aside. Come to HIM. Not to me or any other. Only He can save you.
No wonder that after making great promises to the gentiles, if they will but repent, the angel cries out "wo be unto the Gentiles!" They won't receive: 1) the Gospel, neither 2) the testimony of Jesus, neither 3) the prophets sent to warn them and the message given to them, neither 4) the everlasting covenant offered to them.