Darwin’s theory is useful, indeed, essential, for understanding the patterns of biology, from the nested similarities between different animals, biogeopraphy and the fossil record - the observations that originally made evolution the Millenium Problem of the 19th Century - to genetics and molecular , as well as many, many oddities. In the immortal words of the great evolutionary biologist and theist Theodosius Dobzhansky: Nothing in biology makes sense except in the light of Evolution.
Even if you do not see knowledge as being valuable in and of itself, as you probably do, it should be blatantly obvious that such a fundamental insight into the nature of life is beneficial: We are living beings that most consume living beings and/or their products (whether the by hunting, gathering and scavenging or for the last few millenia crops and livestock we cultivate and purposefully breed ourselves)* to sustain ourselves and are under threat by many living beings and/or their products (predators, parasites, gerns, toxins)*; and that’s leaving aside all the way that we gain materials and medicine from other living beings, the ways we have living beings work for us even today or the many, many, many different ways we gain enjoyment from living beings, let alone the fact that we exist in the context of a planet shaped by life, including ourselves. Understanding the fundamentals of life obviously has many applications in agriculture and medicine. One particularly direct application is epidemology.
* note that those two groups are not mutually exclusive.