I've never liked this whole "One" business. It started with windows 8 on the PC. The same flat blocky interface with the metroscreen/start screen and the apps. It looks like Microsoft went back 20 years to some sort of primitive graphics. ... I think this OS is trying to be one thing on everything and it sounds like an interesting idea in theory but seeing it in practice I don't like it.
"It looks like Microsoft went back 20 years to some sort of primitive graphics."
Doing away with Skeuomorphs is inevitable and advantageous. The beginning of any intuitive interface must be based on known representations - the manila folder icon, for example, representing a logical arrangement of storage. As user familiarity with those interfaces surpases that of the skeuomorph, the purpose of the skeuomorph is lost and better representations may be available. In the next generation, will the "phone" icon make any sense to someone who has never even seen a phone like that? These things should evolve. Microsoft understood that a sea of icons with 3D effects is just another skeuomorph... "oh, it looks like a 3D button... I guess we're supposed to press it". As everyone becomes familiar with the behavior of such interfaces, the need to represent real world objects diminishes. So over time, we ought to see a move toward less skeuomorphic designs.
To answer the question of UI consistency across devices/screens, we ought to consider why Windows became the dominant OS in the first place. Computers were expensive, and not yet ubiquitous in homes. Windows targeted BUSINESS users. As more capabilities became available and hardware prices fell, consumers went along with the OS they were already familiar with at work - Windows. The average user does not want to learn new operating system paradigms. The tile interface design is a result of developing interface sizes and shapes that can conform to any presentation/spec/screen size. Flat, non-skeuomorphic, adaptable and consistent experiences rather than learning a different interface everywhere.
You don't need the Windows 8/10 settings UI because you have control panel? Then you have to know both control panel and a different UI for phone or tablet where control panel is poorly suited. One place, one paradigm, for settings on all devices is clearly ideal. The only catch being that it takes time to build out a new UI before you can truly be rid of control panel.
Don't like a lock screen on a desktop? Is it not simply an improvement on the old "ctl-alt del" lock screen most of us are familiar with in the workplace, now also consistent with tablets and phones? This isn't a bad thing.
As for talking to Cortana, no one said you have to. There's the box. Type in it. Everything you can do with your voice you can do with text. It's certainly an improvement upon previous versions of windows "Run/Search" prompt.
"There should be nothing mobilish on a non phone device that uses a mouse or is in a fixed location for example."
And what then do you do when the line blurs? Should there be nothing mobilish about a Surface because it can have a keyboard and mouse attached? Should your phone project a phone screen to a larger display? Of course not. You'll realize your folly and probably do what Microsoft has done: try to create a consistent UI across different use cases and capabilities, and build in small adaptations suitable to a given use case or... mode - ie continuum. An interface that allows a phone to behave as if a desktop when suitable, or a Surface to adapt to being used like a laptop vs a tablet (tablet mode).
It is the flexibility of the simple tile design that allows such a vast range of use cases and consistent display. They have a good design language. Now they just need to keep refining and improving. I would personally like to see them categorize apps by default and allow customization - allowing the user to swap between categorized and alphabetic on the "all apps" display. They could also allow custom colors per category, and this would make a lot of the app arrangements on the start screen more attractive, as people tend to group apps by function... "news", "office", "social" etc.
If I ever leave WP, it won't be due to design. They have the right idea. If I leave, it'll be because they are simply too slow to compete on features. Mirrorlink has been talked about since 2012, yet we still have no Mirrorlink. When your feature implementation is slower than the auto manufacturers, who are notoriously slow, you have a real problem.