While it's clear that Win RT bombed, it was IMHO a step in the right direction: Make Windows simpler, make it work more like the smartphones and tablets that have been such a sales success since the last decade.
Trouble is: how to deal with the legacy applications (cue the appy app guy). Getting everyone to use the MS store looked to me like a good idea, as long as there was something there worth getting. Yes, other software houses would be annoyed with paying MS a cut of the sale, yes they would be forced to develop according to some sort of valid standard... but that's exactly omitting these things that makes the Win32 ecosystem of the XP era such a PITA and a great environment for malware and bad quality applications
I thought that in the same way that Apple kept on a solid and worthwhile market share with a few select partners and their own multimedia applications, Microsoft can/could do the same, with Office and a few good games for Windows and Xbox.
The way RT was made and marketed, it looked like MS was taking things away from the userbase without giving much back. Yes, ARM SOCs and battery life were interesting but not unique; Windows 8 UI was well suited for that device, but hated by the userbase that is happy to experiment with Android, Linux, Mac OS and iOS, but are vocal about everything and anything that MS changes in their core product lines. This relationship status is "it's complicated"
For now, it looks like Lumia goes to the pile of brands that disappear, and Windows is just Windows 10, on whichever device you might want to use it. In the same way that certain apps won't download from the Google Play store if your device is not compatible, you'll find the same when trying to run apps for Windows 10 mobile that were actually just made for Windows 10 desktop/x64/whatever. It will probably work out well if MS can make their 1st party apps good enough to hold on to some sort of valuable market share (and that's probably got to be xBox & gaming related otherwise iOS and Android gaming will also leapfrog MS in that arena, while everyone is busy comparing Xbox with PS4 and Nintendo). The difference between this time and the 90s is that this market share will be of rent/licence paying customer, not a 90% of a market with a smaller % of people actually spending money. So here's to hoping that the Surface tablets, the xBox with universal appps (aka headless imac), the Surface phone and Surface AIO have something worthwhile to run on them, besides Office and a browser.
All that is to say that IMHO, running X86 Windows applications on a yet smaller form factor scores a big fat meh from me.