So you don't have an answer to the following question?
Didn't Jesus raise Lazarus from the dead by a spoken word of authority? So why did He not defeat death by His word of authority & instead die on the cross in order to defeat death?
God is the one who pronounced the sentence of death in Genesis 3 and in fact stationed angels at the gate to Eden so that mankind would not have access to the Tree of Life and "Live Forever".
IF the entire problem to be solved was "please speak death to be at an end" then it could have been "ended" as soon as it began - in Gen 3.
Christ's death on the cross did not save mankind from the first death - He died to save "whosoever will" from the second death -- the one we see in Rev 20.
Christ said this of Lazarus
1. "Our friend Lazarus sleeps... I go that I may wake him" John 11.
2. He also says "Lazarus is dead"
3.And He says "he who believes on me shall never die".
His first statement speaks of the condition of man in death. Also found in 1 Thess 4:13-18
His second statement refers to the first death - as we find it in Romans 5 and it applies to all mankind, the saints and the wicked.
His third statement refers to the fact that Christ pays our debt of sin in the second death (of Rev 20) so that anyone who accepts the Gospel is spared having to pay that debt.
Death is the 'last enemy" to be conquered - 1 Cor 15.
And in Rev 21 we see "no more death" -- which happens right after the Lake of Fire event of Rev 20 ends.