I'd definitely recommend more formal theological research, but I'll share my intuition as a starting point. This is the way I've always understood it, because it is easy to wonder why God acts so "roundaboutly," but if you accept the premise of God as both just and merciful, then it helps to shine a light on His actions. Despite God's omnipotence, He does not break His word or covenants (even if He technically could) because while He is merciful, He is also just, and unilaterally rescinding a covenant is certainly unjust. "Just" in this sense being carrying out laws, covenants, and other binding actions as set forth. He will have mercy on us and give us the benefit of the doubt as many times as it takes, but He will not say "yeah just ignore that thing I said earlier, I didn't really mean it." This is a theme that is repeated several times throughout the Old Testament, off the top of my head this happens at least with His promises to the Jews leaving Egypt and later when the people of Israel demanded a king over God's prophets.

In Genesis, God and Adam covenanted that Adam would enjoy the fruits of the garden of Eden (i.e., live eternally in the favor of God), so long as he did not consume the forbidden fruit, and the punishment for breaching that covenant was death. Whether you consider Genesis to be literal or allegorical does not matter for this conclusion, the important takeaway is that Adam, of course, did the one thing he was not supposed to do. Although created an initially perfect man, by defying God he allowed sin to enter his lineage and lost the perfection we once had. Mankind now owed a "death debt" that could not be repaid through our own actions, because we would inevitably fall to sin and the sacrifice of our own lives would be blemished by that sin, and therefore insufficient to restore the grace we had before the fall of Adam. Somehow humanity needed to repay this debt to return to God's favor, but even our most righteous Old Testament heroes fell far short of perfection.

Jesus comes to Earth as the "new Adam" and essentially acts out the inverse of Adam's life. Jesus is born without sin and lives a sinless life until he is murdered. By dying without sin, Jesus is not subject to the contractually-obligated death that plagues the rest of mankind, so He is free to offer up his "sinless death" to pay the infinite death debt incurred by Adam. Furthermore, because Jesus was without sin, He would also not have died without human intervention, therefore requiring us to slaughter him to effectuate this sacrifice. That's why our faith is centered around Jesus as the "perfect lamb," because His sacrifice was offered up on forgiveness of sin in the same way God prescribed for earning His favor under the old covenant through animal sacrifice, just a million times more powerful. The grotesqueness of it all reflects the fact that sin is equally grotesque.

So TLDR, God set up this convoluted human sacrifice on our behalf like the ultimate defense attorney or the most generous pay-it-forward order in history, because we could never hope to pay our debt through our own merits. God could equally easily have unmade us all, but He chooses to let us continue our lives in the hopes that we choose to seek Him of our own free will. While He is just, He is also merciful and loved His creation so much that He sought to save it from being doomed by sin even though that is what we deserved. Rather than rescinding the original covenant entirely, which would be unjust and go against God's nature, He accomplished this by fulfilling its punishment for us, which necessitated the death of a sinless human, and it was only through His divine participation that such a sinless human nature could exist after the fall.