The hardware was never the problem. Lots of great devices shipped with Windows Phone.
(Disclosure: Microsoft employee)
I wasn't able to select a Windows Phone. There were several models but none of it made an explicit accent on sound quality. As a last resort I looked to external DACs and it turned out that Windows Phone didn't support them either.
I just went and bought a second hand iPhone 6 with a good discount. The sound quality I got from it was decent and I became a happy Apple customer one more time (had iPhone 4 and other Apple gears before).
So a statement that the hardware was never the problem is a bit of a stretch. Everything accumulates pretty quickly and every detail has an impact.
Regardless, my point wasn’t that the hardware was perfect for everyone or every use case. The point was that there were premium Windows Phone devices before the 950 showed up. The 950 arrived after the end state for Windows Phone was pretty obvious.
The point is that everybody is a different niche. If you start this attitude that feature X is uncommon and not worth the effort, then you do that for a thousand feature X's, eventually you make a product for no one and since you can't predict what niche feature X will suddenly become more important later, the future doesn't happen on your platform.
I have talked to far too many people at MS who have exactly this dismissive attitude about every single feature.
As a dev (at Microsoft), I’m well aware of the potential risk of dismissing features. However, I’m also aware that features are not free. Everyone who actually ships has to make tradeoffs. You can’t ship every feature so you have to cut ones that you think are low value (to the customer or the business, depending on how you look at it).
I don't think the whole answer fits in a comment box though. If you have interest in learning more offline I can explain it further.
Continuum was to be the killer feature but they shot themselves in the foot by releasing the Lumia 650 with such mediocre specs that didn't support it.