I just want to drop in and call out “death is a design flaw” specifically. It is not. Without death, there can be no evolution, and any change to the environment is extinction.
The mountains seem eternal, but there were forests before many of them, and though the trees will be different in the distant eons when the mountains are worn to nothing, the forests will live on.
Oh, giving ourselves endless lifespans is a fine endeavor. We’ve got plenty of ways to adapt to changing environments without changing our bodies, and we’re pretty close to being able to do that without dying and evolving anyway. Shit might get weird, but it always does with us.