It’s worth noting that some of the latter did not jump directly into a PhD program but rather completed a MA along the way – the Dickinson grad at Columbia, the UGA grad at Oxford, the UPS grad at Columbia, the College of Charleston grad at UGA, the Alabama grad at Notre Dame, etc.
I would never say that it’s impossible for a student from a less selective college to get into a good PhD program. It’s simply a bit more difficult, and a postbac or MA somewhere else is often very helpful.
In any case, as @Midwestmomofboys noted, this depends a lot on the faculty you’ve worked with and the recommendation letters they write for you. There’s no doubt that there’s some amazing scholars at moderately selective institutions. A motivated student who studied, say, Linear B and Mycenaean archaeology with Dimitri Nakassis at CU Boulder, Cypriot/Persian studies with Nicolle Hirschfeld and Mark Garrison at Trinity (TX), or comparative Indo-European linguistics with Jared Klein at UGA may well have a far better shot at a good PhD program in Classics than someone who majored in Classics at a highly selective school like Pomona or Vanderbilt but didn’t particularly excel.
