Why doesn’t the Lord appear to man and work in a spiritual body when He comes back in the last day?

Almighty God and man.

The answer from Almighty God’s word:

    “God of the last days principally uses the word to make man perfect. He does not use signs and wonders to oppress man, or convince man; this cannot make plain the power of God. If God only showed signs and wonders, then it would be impossible to make plain the reality of God, and thus impossible to make man perfect. God does not make man perfect by signs and wonders, but uses the word to water and shepherd man, after which is achieved the complete obedience of man and man’s knowledge of God. This is the aim of the work He does and the words He speaks. God does not use the method of showing signs and wonders to make man perfect—He uses words, and uses many different methods of work to make man perfect. Whether it be the refinement, dealing, pruning, or provision of words, God speaks from many different perspectives to make man perfect, and to give man a greater knowledge of the work, wisdom and wondrousness of God. When man is made complete at the time that God concludes the age in the last days, he will be qualified to look upon signs and wonders. When you have a knowledge of God and are able to obey God no matter what He does, you will see signs and wonders, for you will have no conceptions about the reality of God. At the moment, you are corrupt and incapable of complete obedience to God—are you qualified to see signs and wonders? The time that God shows signs and wonders is when God punishes man, and also when the age changes, and, moreover, when the age concludes. When God’s work is being carried out normally, He does not show signs and wonders. Showing signs and wonders is supremely easy, but that is not the principle of God’s work, nor is it the aim of God’s management of man. If man saw signs and wonders, and if the spiritual body of God were to appear to man, would all people not ‘believe’ in God? I have previously said that a group of overcomers are gained from the East, overcomers who come from amid the great tribulation. What is the meaning of such words? They mean that these people who have been gained only truly obeyed after undergoing judgment and chastisement, and dealing and pruning, and all kinds of refinement. The belief of such people is not vague and abstract, but real. They have not seen any signs and wonders, or any miracles; they do not speak of abstruse letters and doctrines, or profound insights; instead they have reality, and the words of God, and a true knowledge of the reality of God. Is such a group not more capable of making plain the power of God?”

from “All Is Achieved by the Word of God” in The Word Appears in the Flesh

The Recitation of Almighty God's Word "God Is the Source of Man's Life" (Excerpt, Stage Version)

    
     Almighty God says, "God created this world and brought man, a living being unto which He bestowed life, into it. In turn, man came to have parents and kin and was no longer alone. Ever since man first laid eyes on this material world, he was destined to exist within the ordination of God. It is the breath of life from God that supports each living being throughout his growth into adulthood. During this process, none believe that man lives and grows up under the care of God. Rather, they hold that man grows up under the love and care of his parents, and that his growth is governed by the instinct of life. 

Resolve to be Born Again - "Offer Love to God" (Official Music Video)

God took on flesh, came to live among us.

Through all disgrace and shame, He gave us salvation.

But I did not know or understand Him, full of grumbles.

How His heart grieved at my rebellion and resistance!

Dear Almighty God, You don’t remember my faults.

You’ve endured all my rebellious ways but offer grace once again.

Knowing You raise me up, I’m covered with great shame.

How unworthy I am to receive Your love!

The Hymn of God's Word "To Bear Witness for God Is Man's Duty"

I

God bestows you with life; it's a gift you receive from Him. And so it's your duty to bear witness to Him. God gives you His glory, His life the Israelites didn't have. And so you must devote your life and youth to Him. You've got God's glory, so you must bear God's witness. It's ordained.

II

It's your good fortune to be given God's glory. And so it's your duty to testify to His glory. If you believe in God only to gain blessings, His work won't be meaningful, and you won't fulfill your duty. You've got God's glory, so you must bear God's witness. It's ordained.

from Follow the Lamb and Sing New Songs

From in The Hymn of God's Word "To Bear Witness for God Is Man's Duty"

The Hymn of God's Word "God's Disposition is Lofty and Grand"

I

God's wrath is that unrighteous things are here to harass mankind, that darkness and evil have their being, as do the things that chase away the truth, and that there are things against the good. His wrath is the symbol of the end of all bad things, and even more the symbol of His holiness, the symbol of His holiness. God's delight is righteousness and light coming into the world, is the destruction of darkness and evil. His delight is bringing light to mankind, and beauty into their life. His delight is righteous; it is the symbol of all things positive, and the symbol of the auspicious, and the symbol of the auspicious.

Concerning the Bible (2)

The Bible is also called the Old and New Testament. Do you know what “testament” refers to? The “testament” in the “Old Testament” comes from Jehovah’s covenant with the people of Israel when He killed the Egyptians and saved the Israelites from the Pharaoh.

Since the Lord Jesus and Almighty God are one God, can’t I also be saved by believing in Jesus?

The answer from Almighty God’s word:

“To man, God’s crucifixion concluded the work of God’s incarnation, redeemed all of mankind, and allowed Him to seize the key to Hades. Everyone thinks God’s work has been fully accomplished. In actuality, to God, only a small part of His work has been accomplished. He has only redeemed mankind; He has not conquered mankind, let alone changed the ugliness of Satan in man. That is why God says, ‘Although My incarnate flesh went through the pain of death, that was not the whole goal of My incarnation. Jesus is My beloved Son and was nailed to the cross for Me, but He did not fully conclude My work. He only did a portion of it.’ Thus God began the second round of plans to continue the work of the incarnation. God’s ultimate intention is to perfect and gain everyone rescued from Satan’s hands, which is why God prepared again to risk dangers to come into flesh.”

from “Work and Entry (6)” in The Word Appears in the Flesh