From the standpoint of simple history I know you're right, but there's an odor of the Myth of Progress about your comment that's unattractive. After all, are we to say that painting is a continuum of progress, a line forever moving onward and upward? Are we to say that later painting (or literature, or culture, or politics) is superior simply by virtue of its later date?
The author of the article posted comes down hard on Byzantine painting because she doesn't know or care what it was about. To find it lacking because it's "unnatural" and fails to depict ordinary people is to miss the point entirely, begging the question of what it was for (a highly-evolved representation of precise theological ideas is the answer, btw). The author assumes that painting is properly all about naturalistic illustration -- a concept as utterly alien to the Byzantines as it is to the mainstream of painters today.