This may be a rather simplistic view but many of the problems appear to have been exacerbated by Boeing trying to implement FBW-like features on a non-FBW aircraft by modifying systems that were never intended for this kind of application? The difference between the 737 family and the A3xx one is stark in this respect.
Given that Boeing have built very successful FBW aircraft, both military and civil, they must be kicking themselves that they didn’t use that knowledge and experience on the 737. Yes, it has a cost but nothing like the one they are having now...