I believe one of the problems (not the only problem) is that there has been no guiding strategy or strategic vision as to how ND should play football to maximize its natural strengths and minimize its natural constraints. We see this since 1996 in...
...Hiring a supposed defensive guru to maintain continuity (who then threw out that "archaic" offense for something much less productive)
Then hiring a WCO coach
Then hiring an NFL OC
Then hiring a supposed run 'n' shoot guru
There has been no standard approach to the type of football ND should play that maximizes its advantages - just grab bagging. And notably most of our coaches have been grab-baggers.
Not that Michigan should be a model, but they basically had the same approach to football for 40 years across 3 coaches, it worked for them, and they had remarkable consistency. They went away from that model with a fancy spread guy, and it was a disaster. It seems they are going back to that old model now.
The AD (or someone working for him) should be involved in developing an overall football strategy that considers the types of players ND has advantages in recruiting, based on location, academics, whatever, and then hire a coach to build a program around that. What 4* and 5* player positions tend to come out of Catholic prep schools? What positions tend to score highest on the wonderlic for the NFL draft?
For example, I don't believe ND ever has difficulty recruiting top-flight OL, QBs, TEs, FBs. Set a strategy that seeks to emphasize those positions on offense and hire a coach to execute this. Consult with football experts to inform this.