I definitely did not get the impression you were saying "the PHB in its entirety, including tieflings and dragonborn" from what you said. Especially since you specifically used the phrase "old school world" immediately before talking about Exandria and the character choices of the Critical Role crew. I did not get even the slightest notion that you were trying to capture the whole of the PHB by saying that. In fact, even going back and looking at the post you responded to, it very much seemed to me that the intent WASN'T that the whole PHB list was on offer, but rather that a much smaller subset (typically the so-called "core four") were it. At least, the implication of the "the same 5-6 settings" line, as it reads to me, is that people are sticking to settings with extremely long already-defined history (as in, literal decades, plural, of regular play) where it may be just humans in one, just the core four in another, etc.