Too much academic work or management responsibility, they call you overqualified. To little: they say you aren't trying.
Enthusiastic for a low end job: we shouldn't hire them because their expectations are too high. To low of energy: they aren't the right fit.
This goes on and on and on as hirers act like their individual set of criteria bias are obvious -- likely because the interviewer themselves has limited experience.
Most people do best when they are told what to do in blind situations. Help them out with a few tips on what to expect and I'm guess you'll find much better applicant quality.
A double digit percentage of the resumes I see have spelling and grammatical errors in them. How hard is it to spend a few minutes checking over a document that is pretty key to your career?
Unless you're working in publishing, I'd pay less attention to trivial errors than to evidence of an ability to get useful things done.
People with strong resumes and strong interviewing skills just don't apply and interview all that often.
People who are weak at the resume stage send out a LOT of resumes. People who are weak at interviewing fail to succeed at a lot of interviews.
Therefore, the randomly chosen resume and randomly chosen interview candidate are well below the median of all workers in the field.