Well, the imagery is intended more as an emotional way of coping with grief than a precise conceptual tool. But to be a bit more exact, the way I interpret death is not literally extinction of us as a species, but the deaths of many individuals, animals and our way of life 'as we know it'. Reducing this to mere change seems wrong - it ignores the aspect of loss which isn't exactly the same as change, so I don't find that meaningless or watered down at all.

Honestly I personally don't really care about whether humans go extinct or not. I don't find the existence of us as a species intrinsically valuable, even though I do find individual life, when it's there, very valuable. It's the suffering I'm concerned about. That's why the adaptation story doesn't do very much for me.