If you want a perpetual winner, the best chance is to go out on a high like Jim Brown, Michael Jordan or Jerry Seinfeld. Stay in the game long enough and your overall performance is likely to gravitate towards the probable outcomes of the event (in the case of Football 50/50).
 
Yes Coaches struggle and yes many of them perform below par for a long time (and then I think it makes sense to change). I’m not sure Norv is in that hopeless category right now. Yes he has lot of things to work on, like say pass plays with more than two receivers in the route. Or running plays that can actually get outside the tackles. A defense that can send five players rushing the QB on every play and every situation. But just like players need to practice and improve so do coaches.

Now if we flip the table, we could look at AJ under that same light. It seems like AJ has quite a bit to practice too.
   
Finding talented line personnel (yes I know he found Deilman & McNeill but we need more of that magic)
Like balancing skills and line personnel to get the optimum team.
Learning how to be GM w/o undermining the authority of the HC
Learning how to work with and encourage the most talented and famous players in the game.
Learning how to work with character issues and events, and mentor these troubled players away from the off the field trouble (I think that is the real magic of the New England Patriots).

AJ is the guy with more on his plate if this team is going to regress back towards the mean.