Re: Management vs. engineers? It's not black and white.
The recent news from SpaceX shows an outfit which is run according to the principles of good engineering management.
I have to disagree with you. As you say their last failure was down to poor quality control practices which lead to a below-spec strut being launched, according to their own publications. And prior to this launch they're finding problems with a very cold throttle valve.
In this day an age in no well run engineering environment launching rockets (and aspiring to launch people) should the strength of a vital strut be unknown, or a vital throttle valve be found to be sticking that late into the launch process. It's not like the temperature profile of a valve was going to be unknown before they filled the thing up with cryogenic fluids.
Fundamentally speaking SpaceX are not carving a new pathway for how these things are done. NASA and the Russians did that, and Ariane too to some extent, working out that total quality control really, really matters. On a machine where every part is essential, it is essential that every part is spec'ed, built and tested to ensure that it works as needed.
To me it feels like SpaceX have found that there are not huge improvements to be made in design (they kinda tried that, turns out a lot of rockets are fairly efficient thrust / weight) or manufacturing (they tried that, turns out you cannot make the manufacturing process a lot cheaper). If you can cut QC processes, that's a big saving (and may be they've been trying that). If you can re-use large parts of your rocket, that too is a big saving. Their recent success is a big step towards potential cost reductions. They can consolidate that advantage if they apply QC sufficient to make it routine, not lucky.