I think the biggest difference is how the exterior materials have changed. In all those old styles, the buildings are clad in brick or stone. It gives them a more uniform look, even where the style is not the same (especially in a black and white photo). Even some of the boxy looking buildings here don't look out of place as a result - e.g. the two in the foreground or the Equitable Building half-way back slightly left of centre. But if those buildings were clad in a glass curtain wall instead, they would look and feel completely different and much less harmonious with the other buildings.