That statement comes from me, a life-long student and teacher. What do I mean?
Very many can create an academic product: cite many sources, use many footnotes, follow the desired format, use the jargon of your specialty, demonstrate that the general public cannot understand you--and, presto, you have created another academic product, whether in the form of a book or commentary or dissertation. And often you can find an academic institution to bless the final product.
We often take these external markers as sufficient for a demonstration of insight, intellect, and useful analysis. We are often wrong to do so. While, in academic settings, most of the above markers are necessary in order to obtain a degree or tenure, the customary markers of the academic product are certainly not sufficient to produce the valid conclusion that the product is authentically intellectual, rather than being merely a mime of the intellectual.
What external markers might indicate the real thing--genuine intellectual insight?
1. The end result is understandable and explains its use of technical terms;
2. The product has a clear and logical structure--the reader can follow the train of thought, even if the route is complex;
3. The product addresses a non-trivial issue. In the humanities, the issue should address in some way wisdom for living and for understanding the world (two types of wisdom which are profoundly connected to each other, as all forms of wisdom are).
4. The writing shows how a non-biased, non-committed reader can honestly reach the same conclusion. The writing is persuasive to the non-committed.
Given those markers of genuine intellectual insight, many academic products fail the grade.
For example, in the area of theology, we often see (as we also often see in legal analysis of all kinds) that the writing is simply the demonstration of a foregone conclusion. What is better is to show the reader how honestly engaging the data and the sources in a wide and comperehensive manner leads to the suggested thesis or conclusion.
Start with the sources then reach your conclusion, not the other way around. Approach the sources with a wide and liberal cast of mind by paying attention to all clues not just those which advance your preferred conclusion.
Often, what is presented to us in books is not a search for truth but a justification of a pre-existing view or bias or even a mere apologia pro vita sua (a self-defense) of some kind. The justification of a pre-existing view or bias can easily be transformed into an academic product, but still falls short of being genuinely intellectual.
Of course, there is an audience for the pseudo-intellectual academic product. Many simply desire a confirmation of their views and are willing to pay for it in print or via other forms of media.
The intellectual shows us the steps of thinking, the path of grappling with questions. Many are uncomfortable and impatient with the twists, turns, and repeating spirals of what is truly intellectual. They prefer a straight and snappy path to a sedating conclusion. They have their reward. Caveat emptor.
(Image depicting Socrates and Plato in public domain)