Lost in Time and Space

The novel is good, but the author went astray in order to be thrilling. Aliens released biological weapons in order to wipe out the people on earth. As a result, the monsters transformed by the biological weapons became intelligent, had strong combat power and unified command, and were smarter than humans. So this biological weapon is of no use. It destroys humans and then creates a species that is more difficult to deal with than humans? The species created by biological weapons should be continuously killed and destroyed without thinking. In the end, there will be only one left in the world, and the alien space-based weapons will directly destroy it and occupy the earth. Otherwise, is there any point in developing this weapon?