I would argue that the pronouns make perfectly viable subjects. For example, the leading "It" in the professor's sentence clearly refers to subjects already defined in previous sentences, and so does not need to be defined again. In general, pronouns serve as a handy form of shorthand to avoid having to define the subject (or object) in every sentence. In some cases, the pronoun serves as a filler since we cannot have a sentence without a subject--for instance, we must say "It is raining," but what, in this case, is the "It"?
I am not against pronouns in general, of course. However, when the antecedents are either not identifiable or are vaporous, ill-defined concepts, the pronoun simply makes the whole caboodle even more diaphanous.
(I know, I’m getting goofy ;-).