I fully disagree. There are so many examples of animals that once de-facto disappeared (like huge sea-lion colonies, same for turtles, reintroduced american and/or european bison, black footed ferret, arabian oryx, hermit ibis, wolves, ...) and then came back, to restore their original biological role. You cannot release a mammoth into central park and hope that it just works. But nobody is trying to do that.