The sellout streak is important but that too is losing its Lustre. Losing has a way of making some things not seem as relevant.
Seems to me this may not come down to thr head coach entirely. Granted, Tom's success will never be repeated. It was also done at a different time so comparisons are difficult. Saban changes coordinators and there is little noticeable change.
I submit thr head coaches since TO have all been good to very good. Two problems plagued the program at various times. One is thr quality of assistant coaches. Where would Calahan have been had he jettisoned his D coordinator? Bo hired a golf pro and Riley probably had a good D coordinator and made the change to Diaco that was a disaster. Not getting into why that was done.
Then throw in recruiting holes. You are not always going to have Suh type players but the drop off can't go from 10 to 5 overnight. It seems over the last 20 years we have not had complete teams. A QB that could run like the wind but not throw and when they get hurt, there is nothing waiting behind them.
Now you are seeing thr problem with OL and DL and those holes. For many years we have one hole or another. Poor coaching or poor players or both. It starts with very good, note I didn't say great coaches. They will be great on average if they work together and develop the kids.
It is not a big secret as to what it takes to win, every coach knows that. And to ruffle some feathers, better clock management and calling the right plays are not the overarching problems. Alas, it won't matter for a few years you will see play calling as a problem each week, or the refs or scheduling by the B1G. Those are all overcome with good overall coaching in all the assistants and that will lead to better players and mistakes go down and play calling miraculously gets better.
This is going to take some time I am afraid. But we should see the improvement. That is just MHO.