Modernity is described by its philosophical critics as the period beginning in the 17th century, called the Enlightenment, to the present. Anscombe's essay "Modern Moral Philosophy" has been credited by both MacIntyre and Hauerwas as the first systematic critique of modernity's moral incoherence, which they all attribute to the attempt to substitute some universal First Principle in the place of a now-domesticated God. The problem, according to these philosophers, is that none of these attempts has been successful, which has ceded the field of morality to law -- which is administered by a technical bureaucracy that is self-serving and narrowly utilitarian.
The main reactions of modernity to the void left as religion lost its power over the modern psyche, according to these three philosophers, are threefold. First, there is the duty-based morality that is usually associated with the philosopher Immanuel Kant. Second, there are utilitarian ethics, often associated with Jeremy Bentham and John Stuart Mill. Finally, there was the individualist reaction of Nietzsche -- the German philosopher who found both rule-based (deontological) and consequence-based moralities (consequentialist) to be contradictory and hypocritical -- and who said individuals who had the power would make their own moralities.
According to these philosophical critics of modern morality, the first two perspectives were logically incoherent because each is based on an idea of human nature that is abstract -- uprooted from any specific time and place. The attempt to devise a universal, abstract account of morality cannot be fitted to real humans, who are always situated in specific times and places that are more complex than any abstraction can match. Nietzsche's hyperindividualist account -- while it appears to critique the other two, it is also attempting to generalize about human nature -- is unacceptable because it leads to nihilism, a belief that nothing has any meaning, and so it cannot be the basis of any moral schema.
The Kantian scheme is one where rules supersede the individual injustices they might cause. The utilitarian scheme -- which looks only at outcomes -- might suggest it is alright to execute a few innocent people as long as it improves the safety of society as a whole. These contradict one another, and many people rely on both forms of logic without recognition of the contradiction. Moreover, no one is obliged to accept either or both accounts, which means governance -- which is administered by bureaucracies with their own inhering self-interests -- is vulnerable to power, which can switch its rationales between Kantian and utilitarian premises, even as powerful people are motivated by a Nietzschean amorality. This is the state the aforementioned moral philosophers refer to as moral incoherence -- which is the source of moral decadence.