Windows 10 Mobile sort of broke things
I've used a Nokia Windows Phone for about 2 years now, and when I first got the phone (switching from Android) I was really impressed with how well the software ran on such comparatively slower hardware. Windows Phone 8.1 worked really well. Most things "just worked" and you could even overlook the lack of apps because usually some enterprising developer had you covered (or the mobile version of the website ended up pinned to my home screen).
Then Windows 10 Mobile came along. Now my Nokia "sort of" works. Everything sort of behaves as it should. I use Windows 10 on my laptop and I really like Windows 10... And personally I believe UWP has legs (although it's yet to find them). And the 1 developer platform to rule them all is a very good idea (so much so that Google and Apple are both attempting the same). But Windows 10 Mobile needs a little more thought and attention.
I think if Microsoft spent a little time and effort tidying up Windows 10 Mobile, and instead of making a lot of phones create a single "surface phone" that can truly prove the merits of the platform (they've already done that with the surface tablet and surface book) and really stop comparing themselves to Apple and Google (or stop trying to BE Apple or Google) then they could have a really promising platform. Of course that's not going to happen because there's hardly any money to be made in the mobile space for MS.
Microsoft has always been about the software. That's where they made their name, and that's pretty much where their revenue is going to keep coming from. Buying Nokia was a bad move on their part because they're a software company... I think SatNad's ideas of re-focusing MS on software rather than messing around with hardware (with the exception of the surface line) is a good one. And I think they're on the right lines at the moment to try and make Windows the "go to" developer platform - Look at their approach, the idea is it doesn't matter what you're deploying to, you can develop on Windows...
And they should keep Windows 10 Mobile going of course because there's still opportunities out there for it. It certainly could become the new BlackBerry...