Patrick Deneen's argument is that classical liberalism inevitably leads to the radical autonomous individualism, with all its problems, that we see today.
Discussion
I seem to be missing how post-liberalism differs from classical liberalism. The later never precluded the aristocracy or some concept of personal nobility or excellence leading naturally to human hierarchies.
Another way I've heard it described is that once you view harm as more than physical (e.g., discrimination), there is nothing stopping liberalism from becoming what it is today.
This is also a good explainer: https://youtu.be/ot8Eul-nDU4