But why is Airbus so much better ?
OK, seriously though, when it comes to outsourcing, it's because Airbus/CASA rigorously defined systems interfaces and all sorts of other stuff before outsourcing design. I've been a part of the supplier chain there, and it's intense, but it means your part's got a good shot of slotting in the first time.
787 - and a whole truckload of BDS work - it's less "strict systems interface" and more "what is systems interface". You can get decades pass where the part still doesn't fit.
But the problem with the Eight, at least initially, was the way the suppliers were organized. Or, more specifically, how they weren't organized. Boeing had flushed through a half dozen generation of Systems Engineers in the aughties, and no one really had a half chance to get familiar with anything that was laid down before. Suppliers generally took their best guess and went with it - that's where we were, at the time, because it proved completely impossible to make any contact with a person at Boeing who knew what the FMS data bus was . . or, on most days, even what a FMS data bus was. So we guessed either ARINC429 or ARINC664 and got (mostly!!) lucky.
There were also some . . ah, I don't want to say "bad" . . so let's say, "non-technical" SEs . . who advocated for their own vision vis a vis SE and supplier management. In short, this was a giant mish mish, and, speaking for myself, it colored my personal perception of Systems Engineering as a discipline to this day. While you get some real SE rockstars, you also get an epidemic of shysters with mild sociopathy, and it takes good, technical leadership to tell one from the other.
Keep in mind this was . . sheesh . . almost two decades ago, so take it all with a grain of salt.
With that said, a nontechnical SE is a sign of a fundamentally broken system and org. Someone had to hire them for the role. Meaning they were interviewed and deemed fit for the role, likely with room to grow given more experience and opportunities to learn from. While I would say a nontechnical SE is bad st their job, stopping there doesn't fix the problem at all and its important that the context of why they had that job isn't lost.
Moreover though, if my original argument is right, the failing system of regulation will fail slowly (presumably then all at once). The FAA and other bodies involved in the air industry may be broken, but it still takes a kick to push a company over the edge. A company like Airbus could continue to operate extremely well despite the broken system, though I'd argue with enough time they will be hit by it as well.