While it is true that extinction is a natural process that has occurred since the dawn of time, to say that the loss of one species does not necessarily lead to the loss of an important version of the universe is oversimplifying Nikhil's original argument. Nikhil correctly pointed out that plants and animals have a unique experience of the universe and the extinction of a species means that perspective is lost forever. Sure, evolution produces new species over time, but their experiences will never be able to replicate those of extirpated species.
Furthermore, Nikhil's essay was not about fear or about praising extinction in any way. Instead, his point is that every species' unique perspective is vital for a complex and complete understanding of the universe. The idea that any single perspective from an entire species can be replaced by another species' perspective is an offshoot of the popularized thought that one individual can replace another. This model of simplistic replacement ignores the beauty of diversity and misses the point of trying to understand more than one worldview.
Although it is true that some species may be able to survive and thrive in a changing environment, can we really expect them to provide us with the same viewpoint, experience, or perspective as their predecessors? Instead of looking at extinction as a negative phenomenon, why not see it as an opportunity to appreciate and protect what each species has to offer? After all, if we respect and celebrate the varied perspectives brought by plants and animals, we can develop a fuller, richer understanding of our universe. Who knows, maybe we'll find some unexpected gems along the way!