If God’s position is that sin is a condition that makes us humans out of harmony with His law of love, then it’s not clear to me why it was necessary for Jesus to die that I can have eternal life.

Jesus could have come and I accept Him and His teaching and reverse the human neurological brain disorder or “condition” by changed thoughts and behavior.  Not sure I understand why Christ death was necessary in this process to bring me back in harmony with God?

Great question and one I don’t pretend to offer the “final” word on, but anticipate our understanding to the answer for this question will grow through all eternity. I hope others will offer their insights and inspired evidence to help us grow in our understanding. Here are some of the reasons I understand we could not be healed without the death of Christ:

Without the life, death and resurrection of Jesus we wouldn’t have the evidence about God to be won to trust. Nor would Satan have been exposed as a liar, fraud and murderer. God’s government of love, His selfless character and the truth necessary to destroy Satan’s lies would not have been available had Christ not died as He did.

Christ also, in doing this within His human nature, revealed there was no defect in Adam’s creation (no manufacturer’s defect) and also no deficiency in the design for life (law of love), but in fact all defects were a result of deviations from God’s law.

Through the plan of salvation, a larger purpose is to be wrought out even than the salvation of man and the redemption of the earth. Through the revelation of the character of God in Christ, the beneficence of the divine government would be manifested before the universe, the charge of Satan refuted, the nature and result of sin made plain, and the perpetuity of the law fully demonstrated.  –  Signs of the Times, December 22, 1914

Yet revelation of truth alone was not sufficient to fix broken man. The only way to heal the human species was within the brain of a human being – God could not use divine power, external to humanity and inflict, insert, divinely cause a character change, this would destroy the individual and “create” a new entity. The only way for God to actually “heal” the same species He created in Eden, but which was now infected with fear/selfishness, was to take this condition upon Himself, and in His human brain rewrite the law of love.

God possesses a perfect divine nature, angels in heaven possess perfect angelic natures, beings on other worlds are in possession of perfect natures of their order – but after Adam’s sin and before Christ’s victory there was no perfect human nature. Christ came to fix this and, within the species human, restore perfection of character. Divinity can create a new order/species anytime Divinity chooses – but humanity, once infected, could only be cured by the exercise of human choice – free will trust in God. No human, descended from Adam, could accomplish this, but Christ, uniting His divinity with humanity did this work. A human being had to exercise trust in God. A human being had to reject the lies and temptations of Satan. It is this renewed human nature, achieved singly by Christ, that God offers to instill in all who trust Him. We become partakers of the divine nature, through our trust in Jesus.

The reason the Son of God appeared was to destroy the devil’s work. 1John 3:8

The life of Christ is to be revealed in humanity. Man was the crowning act of the creation of God, made in the image of God, and designed to be a counterpart of God; but Satan has labored [worked] to obliterate the image of God in man, and to imprint upon him his own image.  –  Lift Him Up, pg. 48

“In assuming human nature, that he might reach to the very depths of human woe and misery and lift man up, Christ has shown what estimate he places upon the human race. In this work everything was at stake. Satan claimed to be the lawful owner of the fallen race; and with what persistent effort did he seek to overthrow Christ through his subtilty! It was only by the most desperate conflict with the powers of Satan that Christ could accomplish his purpose of restoring the almost obliterated image of God in man, and place his own signature upon his forehead. It was a desperate battle; for Satan had so long worked in league with human intelligencies as to almost completely intercept every ray of light shining from the throne of God upon the human mind. The cross of Calvary alone could destroy the works of the devil. In that wondrous sacrifice all eyes were called to ‘behold the Lamb of God, which taketh away the sin of the world.’ The love of Christ kindles in the heart of all who continue to behold him.  –  General Conference Daily Bulletin, March 2, 1897 par. 17.

Because man fallen could not overcome Satan with his human strength, Christ came from the royal courts of heaven to help him with His human and divine strength combined. Christ knew that Adam in Eden with his superior advantages might have withstood the temptations of Satan and conquered him. He also knew that it was not possible for man out of Eden, separated from the light and love of God since the fall, to resist the temptations of Satan in his own strength. In order to bring hope to man, and save him from complete ruin, He humbled Himself to take man’s nature, that with His divine power combined with the human He might reach man where he is. He obtained for the fallen sons and daughters of Adam that strength which it is impossible for them to gain for themselves, that in His name they might overcome the temptations of Satan.   –  Confrontation, pg. 45

The law requires righteousness,–a righteous life, a perfect character; and this man has not to give. He cannot meet the claims of God’s holy law. But Christ, coming to the earth as man, lived a holy life, and developed a perfect character. These He offers as a free gift to all who will receive them. His life stands for the life of men. Thus they have remission of sins that are past, through the forbearance of God. More than this, Christ imbues men with the attributes of God. He builds up the human character after the similitude of the divine character, a goodly fabric of spiritual strength and beauty. Thus the very righteousness of the law is fulfilled in the believer in Christ. God can “be just, and the justifier of him which believeth in Jesus.” Rom. 3:26.  –  The Desire of Ages, pg. 762

The Lord Jesus loves His people, and when they put their trust in Him, depending wholly upon Him, He strengthens them. He will live through them, giving them the inspiration of His sanctifying Spirit, imparting to the soul a vital transfusion of Himself. He acts through their faculties and causes them to choose His will and to act out His character. With the apostle Paul they then may say, “I am crucified with Christ: nevertheless I live; yet not I, but Christ liveth in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me” (Gal. 2:20).  –  That I May Know Him, pg. 78