There is not a whole lot to glean from Isaiah 21-23. Ludlow discusses some parallels between Isaiah's writings and historical events.
Desert of the Sea
The nation described as "the desert of the sea" is never actually named. Many had speculated which nation it might be. Some think it is Babylon (see OT Student Manual: 1 Kings to Malachi p. 157).
Isaiah's Reaction to the Destruction
In Isaiah 21:3-4, Isaiah is painfully afflicted by seeing this vision of the destruction of the desert of the sea. If this nation is indeed Babylon and if this vicious destruction foreshadows the destruction of the world (Babylon = The World) in the Last Days, then Isaiah's reaction should be another warning to us who live in these latter-days.
Dumah and Arabia
I like what the OT Student Manual says about this. "As Isaiah used the destruction of every major sister nation to Israel as a type of the judgment that is to be administered to the wicked and their organizations in the last day, so he here, almost parenthetically, prophesied the destruction of even the minor nations of the east."
Valley of Vision: Jerusalem
Ludlow points out that "although the Assyrians have already destroyed dozens of Judean cities and take thousands of Jewish captives, the people of Jerusalem celebrate their freedom" (231). The people of Jerusalem make preparations for battle (Isaiah 22:6-11) but she does not remember the most important aspect in preparing for battle: remembering the Lord.
Isaiah rebukes them for making the "ditch between the two walls for the water of the old pool: but ye have not looked unto the maker thereof, neither had respect unto him that fashioned it long ago" (Isaiah 22:11).
We can make all the preparations in the world to fight temptations, but unless we invoke the Lord's help, all our work and preparations will avail us nothing.
Shebna and Eliakim and the Temple
Shebna was the leader of the king's court. Ludlow states that according to some scholars, Shebna was a foreigner. Because Shebna did not have Jerusalem in his best interests, the Lord replaced him with Eliakim.
Eliakim, which means "God shall cause to rise", is also a type for Christ. Isaiah, like many other times, uses language to not only describe the historical figure, but he uses language to describe Christ.
As you read Isaiah 22:21-25, you will note the significance of the language as it pertains to temple ordinances.
Elder Nelson's April 2001 General Conference talk does a wonderful job of explaining many aspects of the temple. He references Isaiah 22 in the following quote, "One may also read in the Old Testament and the books of Moses and Abraham in the Pearl of Great Price. Such a review of ancient scripture is even more enlightening after one is familiar with the temple endowment. Those books underscore the antiquity of temple work" (Russell M. Nelson, “Personal Preparation for Temple Blessings,” Ensign, May 2001, 32)
The concluding "burden" is directed at Tyre. As Babylon is the symbol of wickedness and idolatry, Tyre symbolizes worldliness and materialism (Ludlow 236). Just as Babylon would fall, so too Tyre would loss her glory. Perhaps this means that in the last days as the world and its wickedness is destroyed, so too will the markets and trade systems collapse.