Great coaches come with all sorts of backgrounds. Some of the greatest coaches of all times learned on the job. It does not matter if a coach has a coaching degree from a university or has taken certification classes, if they don't use what they were taught.
Many Athletic Directors use the university coaching degrees as a first weeding out factor in hiring. In some ways this is good, in other ways it is not. There are many coaches that started before university coaching degrees existed. This does not mean they are bad coaches. Many of these coaches are actually very successful and produce outstanding athletes.
Athletic Directors should (but many times don't) look at the individual coach and how they developed skills over time. Have the athletes improved? Every program has strong and weak years, but overall improvement usually is a decent indicator that the coach is doing a good job.
Also, the AD needs to also consider the support and conditions that the coach has thrived under. Many programs have very limited budgets and thus can't produce national championship teams (can't give full rides to the best athletes). However, did this coach greatly improve the athletes that they did work with?
But, as has been said here many times, at many schools, the people who do the hiring of coaches usually go with who they know, even if they have a lot less experience. Most of the time resumes sent in for openings, barely, if at all, get a glance over by hiring committees.
Thus, the key to getting hired is not what degree you have or what certificates you have, but who you know. If you can't get a paid job, find a major university that will let you volunteer. There have been several examples of volunteer coaches, or GA's, that have gotten good positions after a couple of years. Then go to coaching clinics, certification classes, etc. and get your name out there. Make sure the other coaches know who you are.