Academic writing is difficult to read only when it is either covering a topic that the reader does not understand or when it is written without any inspiration.
You might start with a quote from Kahlil Gibran: "If you must indeed be candid, be candid beautifully. Otherwise, keep quiet, for there is a person who is dying in our neighborhood." You can probably find that on the Internet somewhere.
Academic writing is candid, but writers often feel that if they are being candid and obeying the rules (of MLA or APA or CHICAGO, or whatever citation style they are using), that it is not necessary to write beautifully.
When you read a book that is written as entertainment, the writing will be beautiful. When you read a book that was written to instruct, the fact that the author has a purpose other than to please the reader provides an excuse to not bother writing beautifully.
Reading writing that is not beautiful is like listening to awful music.