I have reasons to think that extinction shouldn’t be such a bad thing.
1. Species change is an empirically accepted notion: not only has it happened, it perhaps will happen again
2. The (generic) notion of species change can happen in virtue of the obsoletion of the species or genus, or the environment they persist in.
i. Consider the betamax; it is, compared to other newer media, outdated!
ii. Some species who are now extinct may have won out to their progeny species in some respects (imagine a fight with a dinosaur); however, they probably wouldn’t survive as the environment is vastly different (consider, most notably, vegitation)
3. It may be cruel to resurrect or preserve a species whom which could never live in the native habitat in which they originally came from. With things like deforestation, climate change, urbanisation, we may keep animals from other environments, but we shouldn’t expect them to be the same once we change their environment, nor is it reasonable to say that we are ‘preserving’ them in a very strong sense (but not to say we are not preserving them at all).
4. Change in species may be inevitable; but there are reasons to think that some species will not change; by virtue of human intervention.