My hypothesis: it wasn't really the structure of faces etc. that looked weird to you. You were just baffled in general by the weirdness of watching such an old

My hypothesis: it wasn't really the structure of faces etc. that looked weird to you. You were just baffled in general by the weirdness of watching such an old footage, and "blaming" this on what people looked like was a way your brain rationalized this elusive sense of weirdness away. When we're adults, we've seen our share of old pictures, the sense of wonder weakened, and so the feeling of bafflement is gone. And along with it, the need for rationalizing it off.