What level of specificity is appropriate to the task at hand? What level of detail is it necessary to present for your argument to work? The answers are dependent on the situation in which you are working. But the questions need to be asked repeatedly. It's necessary to get a good fit--and in particular this is important in not allowing the writing to be dragged away from the story that you wish to tell.
What is your writing about? If it is academic writing, it is not about lyrical beauty of the words, nor about the ability to touch the emotions of the reader. Academic writing is about the expression of ideas, of theories, of discoveries, and interpretations; it is about new understandings and new knowledge.
Therefore, writing can be valued by its ability to succinctly express and defend the important ideas, and its ability to efficiently and cleanly develop the argument.
The well-known principle of Occam's Razor suggests that in choosing between theories, the one that is simpler is to be preferred.
But this same principle can usefully be applied to academic writing: writing that is simpler is to be preferred. Occam's Razor can be translated "entities must not be multiplied beyond necessity." Necessary complexity is not to be eliminated. But detail should not be multiplied beyond necessity.
But how, I hear you ask, do you determine what is necessary? Sadly it's a matter of judgment. Writing is about communicating with people, and communicating well and clearly is difficult and a matter of art rather than logic. But the principle can still guide you: "is this detail necessary to the argument?" If you can answer no, then you can cut something. And simply knowing that the principle suggests the importance of eliminating detail can itself do wonders in helping keep the work focused.