I think for the most part the LW-sphere’s attempts to make life like a high fantasy novel in this respect do so by targeting an extremely abstract thing as a villain, such as “death itself”. In this case, it’s only a metaphor intended for motivation, because humans really like “defeating the villain”, and the actual thing being attempted is building, much more than it is destroying—the reasons why defeating an actual literal villain is usually not finishing the job and might actually make things worse don’t really apply, although that doesn’t necessarily rule out that the effort to “defeat death” might have negative consequences, such as those /u/chaosmage has detailed.
I think for the most part the LW-sphere’s attempts to make life like a high fantasy novel in this respect do so by targeting an extremely abstract thing as a villain, such as “death itself”. In this case, it’s only a metaphor intended for motivation, because humans really like “defeating the villain”, and the actual thing being attempted is building, much more than it is destroying—the reasons why defeating an actual literal villain is usually not finishing the job and might actually make things worse don’t really apply, although that doesn’t necessarily rule out that the effort to “defeat death” might have negative consequences, such as those /u/chaosmage has detailed.