Because the world is constantly changing there can never be such a thing as a perfect species. For example, the diseases and parasites that each species has to deal with are constantly evolving to try to beat that species’ immune system, and so it must keep evolving to try and keep up. But all species have been equally affected by evolution. So you can’t really say that a species is “perfect”. Each species has evolved in the way it has because of the environment it has been in.
Good question. In a way evolution is constantly producing animals that are perfect for their environment. So think about how birds seem perfect to fly. They have wings that are the perfect shape, bones that are hollow so they are light, and feathers to keep warm and help them fly.