Here are some relevant quotes:

On 4 May 1842, after President Joseph Smith gave the first Nauvoo-era endowment to a small group of Latter-day Saints, he told apostle Brigham Young that “this is not arranged perfectly; however we have done the best we could under the circumstances in which we are placed. I wish you to take this matter in hand: organize and systematize all these ceremonies.” (https://rsc.byu.edu/archived/joseph-smith-and-doctrinal-restoration/7-joseph-smith-and-restitution-all-things)

Joseph Fielding Smith noted that the “work of salvation for the dead came to the Prophet [Joseph Smith] like every other doctrine — piecemeal. It was not revealed all at once.” (Joseph Fielding Smith, Doctrines of Salvation, volume 2, comp. Bruce R. McConkie, 3 vols., (Salt Lake City: Bookcraft, 1954–56), 168.)

Wilford Woodruff said, “President Young, who followed President Joseph Smith, led us here. He organized these Temples and carried out the purposes of his calling and office. He laid the foundation of this great Temple on this block, as well as others in the mountains of Israel. What for? That we might carry out these principles of redemption for the dead. He accomplished all that God required at his hands. But he did not receive all the revelations that belong to this work; neither did President Taylor, nor has Wilford Woodruff. There will be no end to this work until it is perfected.” (https://www.lds.org/manual/presidents-of-the-church-teacher-manual-religion-345/wilford-woodruff-fourth-president-of-the-church?lang=eng)

On April 8, 1894, Wilford Woodruff spoke of revelation received that clarified how sealing should be done:

“I have not felt satisfied, neither did President Taylor, neither has any man since the Prophet Joseph who has attended to the ordinance of adoption in the temples of our God. We have felt that there was more to be revealed upon this subject than we had received. Revelations were given to us in the St. George Temple, which President Young presented to the Church of God. Changes were made there, and we still have more changes to make, in order to satisfy our Heavenly Father, satisfy our dead and ourselves. I will tell you what some of them are. I have prayed over this matter, and my brethren have. We have felt, as President Taylor said, that we have got to have more revelation concerning sealing under the law of adoption. Well, what are these changes? One of them is the principle of adoption. In the commencement of adopting men and women in the Temple at Nauvoo, a great many persons were adopted to different men who were not of the lineage of their fathers. …

“Now, what are the feelings of Israel? They have felt that they wanted to be adopted to somebody. … When I went before the Lord to know who I should be adopted to (we were then being adopted to prophets and apostles), the Spirit of God said to me, ‘Have you not a father, who begot you?’ ‘Yes, I have.’ ‘Then why not honor him? Why not be adopted [sealed] to him?’ ‘Yes,’ says I, ‘that is right.’ I was [sealed] to my father, and should have had my father sealed to his father, and so on back; and the duty that I want every man who presides over a temple to see performed from this day henceforth and forever, unless the Lord Almighty commands otherwise, is, let every man be [sealed] to his father. When a man receives the endowments, [seal] him to his father; not to Wilford Woodruff, nor to any other man outside the lineage of his fathers. That is the will of God to this people. …

“In my prayers the Lord revealed to me, that it was my duty to say to all Israel to carry this principle out, and in fulfillment of that revelation I lay it before this people. I say to all men who are laboring in these temples, carry out this principle, and then we will make one step in advance of what we have had before. Myself and counselors conversed upon this and were agreed upon it, and afterwards we laid it before all the Apostles who were here … , and the Lord revealed to every one of these men—and they would bear testimony to it if they were to speak—that that was the word of the Lord to them. I never met with anything in my life in this Church that there was more unity upon than there was upon that principle. They all feel right about it, and that it is our duty. … The Spirit of God will be with us in this matter. We want the Latter-day Saints from this time to trace their genealogies as far as they can, and to be sealed to their fathers and mothers. Have children sealed to their parents, and run this chain through as far as you can get it” (Millennial Star, 56. 22 (May 28, 1894): 338–39) (https://www.lds.org/manual/presidents-of-the-church-teacher-manual-religion-345/wilford-woodruff-fourth-president-of-the-church?lang=eng)

In the October 1989 General Conference, Elder Boyd K. Packer said:

Later, speaking on the same subject of temple ordinances, the Lord affirmed again that He will reveal His will to His authorized servants:

“For him to whom these keys are given there is no difficulty in obtaining a knowledge of facts in relation to the salvation of the children of men.” (D&C 128:11.)

That principle of revelation has been with the Church ever since. Those who hold the keys have obtained knowledge on what to do. When changes have come, they have come through that process. The Lord does as He said He would do:

“I, the Lord, command and revoke, as it seemeth me good.” (D&C 56:4.)

“I command and men obey not; I revoke and they receive not the blessing.” (D&C 58:32.)

He told the Saints that when enemies prevented them from keeping a commandment, he would no longer require them to do so. And he said:

“The iniquity and transgression of my holy laws and commandments I will visit upon the heads of those who hindered my work, unto the third and fourth generation, so long as they repent not.” (D&C 124:50.)

The gospel plan was revealed line upon line, precept upon precept, here a little, and there a little. And it goes on: “We believe that He will yet reveal many great and important things pertaining to the Kingdom of God.” (A of F 1:9.)

There will be changes made in the future as in the past. Whether the Brethren make changes or resist them depends entirely upon the instructions they receive through the channels of revelation which were established in the beginning.

The doctrines will remain fixed, eternal; the organization, programs, and procedures will be altered as directed by Him whose church this is. (https://www.lds.org/general-conference/1989/10/revelation-in-a-changing-world?lang=eng)

And, in the April 2014 General Conference, President Dieter F. Uchtdorf reminded us that “Sometimes we think of the Restoration of the gospel as something that is complete, already behind us—Joseph Smith translated the Book of Mormon, he received priesthood keys, the Church was organized. In reality, the Restoration is an ongoing process; we are living in it right now. It includes ‘all that God has revealed, all that He does now reveal,’ and the ‘many great and important things’ that ‘He will yet reveal.’ Brethren, the exciting developments of today are part of that long-foretold period of preparation that will culminate in the glorious Second Coming of our Savior, Jesus Christ.” (https://www.lds.org/general-conference/2014/04/are-you-sleeping-through-the-restoration?lang=eng)