"Single Greatest Mistake ever made in the Entire History of Western Thought" & apparently implicit in Vatican II that caused "the Abortion Industry’s Slaughter of Millions" & "the Judicial Murder of Terri Schiavo"
In my opinion, one of intellectual giants in the Church in the United States is philosopher Edward Feser. I have seen Feser totally destroy, with a devastating intellectual knock out Mark Shea (which is pretty easy), theologian Massimo Faggioli (a bit harder) and on YouTube win an impressive victory over a very intelligent modern philosopher.
Feser says in the bottom of page 52 of his book "The Last Superstition" that abandonment of the medieval Thomistic "developments" of "Aristotelian ideas" brought about the "civilizational crisis through which the West has been living for several centuries":
“How significant is Aristotle? Well, I wouldn't want to exaggerate, so let me put it this way: Abandoning Aristotelianism, as the founders of modern philosophy did, was the single greatest mistake ever made in the entire history of Western thought. More than any other intellectual factor – there are other, non-intellectual factors too, of course, and some are more important – this abandonment has contributed to the civilizational crisis through which the West has been living for several centuries, and which has accelerated massively in the last century or so. It is implicated in the disintegration of confidence in the rational justifiability or morality and religious belief; in the widespread assumption that a scientific picture of human nature entails that free will is an illusion; in the belief that there is a “mind-body problem” and that the only scientifically and philosophically respectable solution to it is some version of materialism; in the proliferation of varieties of relativism and irrationalism, and also of scientism and hyper-rationalism; in the modern world’s corrosive skepticism about the legitimacy of any authority, and the radical individualism and collectivism that have followed in its wake; and intellectual and practical depersonalization of man that all of this has entailed, and which in turn led to mass-murder on a scaled unparalleled in human history. Its logical implications can also be seen in today’s headlines: in the abortion industry’s slaughter of millions upon millions of unborn human beings; in the judicial murder of Terri Schiavo (as Nat Henthoff aptly labeled it) and the push for euthanasia generally; in the mostly pointless and certainly point-missing debate between Darwinians and “Intelligent Design” advocates; in the movement for “same-sex marriage” and the sexual revolution generally; and a thousand other things besides.” [ The Last Superstition: A Refutation of the New Atheism. 51-52]
Independent scholar James Larson pointed to the fact that the Church since Vatican II helped to bring about this "civilizational crisis" by abandoning Thomism:
"Since Vatican Council II, it has been the overwhelmingly prevalent view, especially among the Catholic hierarchy, that the Church must seek a new philosophical and theological basis for its teaching – an approach which will somehow bypass what is alleged to be the “intellectualism” of St. Thomas Aquinas. It has been repeated ad nauseum that St. Thomas’ approach to the faith is static, rigid, rationalistic, and even Pelagian, and that a new approach... is necessary in order to restore some sort of original, gospel-centered “heart” to Catholic thinking and spirituality." [https://www.thecatholicmonitor.com/2019/09/thomism-is-remedy-for-mad.html]