If we're going to talk about death, and particularly if we're going to argue that death is not part of the curse (well, not directly), then we have to start by talking about life. More specifically, we have to confess that we are not eternal beings. We never were.
We were not created to live forever. At least, not apart from the provision of God Himself. Now, when we try to make this argument, there are many who try to say that the whole creation lives through a cycle of life and death - seeds die and become plants; animals give birth and pass away; lions eat impala. And so, if all of nature experiences death, then so, too, must we as creatures of a Creator God. But I think that's a bit more complicated than others seem to want to make it. After all, we do not know if this cycle of death and life existed before the whole earth was cursed or not. Is this the way God designed it or did we doom it to this by our sin?
The much simpler way to answer this question is to look at the other tree in the Garden - the tree of life. Now, remember, there were two named trees in the Garden - the tree of the knowledge of good and evil, of which Adam and Eve were never supposed to eat, and the tree of life, which God feared they would eat from after their sin and live forever.
For some reason, most of us read this and think that one peach would be enough for eternal life, and we start thinking that if we had been Adam and Eve, knowing everything, then we would have just grabbed one of those delicious fruits on our way past the cherubim with the flaming sword. Problem solved, right?
But that's not how the tree of life works. The tree of life is a fruit that is meant to be eaten routinely, perhaps even daily. God intended that man, in search of life, would have to keep coming back to the fruit that God provided for him for this very purpose.
See, it's just extremely hard to believe that Adam and Eve lived in the Garden with God and never once ate from this tree before their sin. It's hard to believe that they would have this glorious tree with this amazing name and this awesome promise connected to it and not partake of it. We can only naturally assume that they had eaten from this tree. Probably a lot.
If this tree, then, provided eternal life with just one bite, then God's concern about them eating from it after their sin is moot. If they've already eaten it, they'd already be living forever, and God would have to come up with some kind of new plan to keep them from living forever with all the knowledge of good and evil.
The only understanding that makes any sense, then, is that the tree had to be eaten from continually, faithfully. Often. That God designed man to live only in dependence upon Him - His provision, His goodness, His grace. If man could not or would not do that, then he would die.
Thus, death was woven into our creation from the very start. It's not part of the curse; it's part of our call to come to Him. It's part of the promise of God of life itself.
Got it? Okay, great. Now, we can go back to talking about death.