Dunning et al.  showed that incompetent people tend to be blissfully ignorant of their incompetence (the Dunning-Kruger effect), lacking both the ability to produce correct responses and the expertise to identify their problems. Incompetent people base their perceptions of performance partly on their own inflated opinions of their skills.
Students must satisfy objective criteria to enter university, and academics are appointed and promoted on merit, so in theory incompetence should be rare in higher education. Of course, in reality many students and academics are very good at some components of their work and not so good at others. Academics in the STEM (science, technology, engineering and maths) disciplines can be highly technically skilled but communicate poorly. Thankfully (from my perspective), most academics with deficient writing abilities (sometimes due to dyslexia, or having English as a second language) are well aware of it and will employ a professional editor to tidy up their work. Nevertheless, I occasionally encounter students and academics who exhibit all the signs of the Dunning-Kruger effect and truly believe their thesis or paper is excellent and requires only minor proofreading rather than a full-blown edit.
Few writers can edit their own work effectively, and I think this is particularly true of academics. This is because they spend a long time thinking about their research, planning, generating or collecting and analysing data and so on, so by the time they come to write about their work for publication their perspective on it can be quite narrow and/or skewed. Papers derived from the hothouse of a PhD thesis are especially vulnerable. A second pair of eyes, especially if belonging to someone not intimately connected with the research, can often be invaluable in picking up breaks in logical flow, insufficient explanations of content, inconsistencies and simple omissions of words. That’s my job!
 Dunning, Johnson, Ehrlinger & Kruger, Why People Fail to Recognize Their Own Incompetence, Current Directions in Psychological Science 2003, vol. 12, no. 3, 83-87