Well, in Rob's defense, he obviously never relied on over-referencing photos!
The problem with Liefeld's art, in my non-artist view, is that he learned to draw from comics. Comics are fine as a starting point but eventually you need to go off and learn perspective and anatomy and how to draw real life stuff. You need to be able to draw "properly" before you layer in the stylization. Look at Jack Kirby, his perspective and anatomy were often crazy as hell but it wasn't because he didn't know better, it was because he made a conscious effort to tweak things for the sake of style and power in the image. And also because he was drawing ten pages a day.