It's like playing a game with all the cheats on. Sure, they let you "win" super easily, but because it was super easy, it stops being fun.
You could still just as easily get hit by a car when you are 90 and look 20. Or 1000 and look 20, assuming that's even possible. What's really interesting is if people could actually prolong their lifespan indefinitely but we have the same limited bodies. Then you'll see people trying really hard to say alive to comical effect.
I think Aronofsky's The Fountain is a really great outlook on death. It is a disease and like any disease we may as well try hard to defeat it. Doesn't mean it isn't very natural.
Hell, if age couldn't kill you, then you could chose your death, which is less random than a heart attack or stroke.
I tend to see human-lifespan rationalizations as simple fatalism. It's okay to think you'd get bored after a million years, but dooming every living human to die because you'd be bored is kind of insane if you think about it.
But you are very mortal and you are at most a few decades old. Your perspective would probably change drastically in your third century or millenia.
It makes conjecture like this as good as worthless because as mortals we do not have the ability to see it from another perspective.
I'd rather have that opportunity than not.
No, if we lived forever, we would have to make a lot more hard choices, because we would have so much more time to be exposed to them.