Sorry to say it, but I think you're missing the point a bit: You're mixing up developers' development and application development. Sure, people will eventually create their 3D part in DirectX, but the first step really does start simple. Not everyone is ready to write C++/D3D code/shaders..
The reason why people liked XNA is because it's C# and (also therefore) easy to use. In C++ you miss a lot of tools that .NET has made available. Stuff like xml parsing, network connectivity, etc. Granted, you can also find tools for that on the C++ side, but those are generally harder to use.
Obviously, each language has it's pro's and con's. But I think that a lot of developers' first choice is C# because you can write a reasonably well performing application in a very short amount of time.
Therefore, I am very surprised to see that Microsoft does not have a solution for quick-and-dirty 3D. Also with this (btw: EXCELLENT!) starter kit, it still requires you to implement a lot of C++ code. Unmanaged C++ code, I should mention; making it hard for people to merge it into their C# application.
Let me put it in another way, by telling you the reason why I ended up at this place:Last weekend I wrote a simple tool to render a 3D surface in a web page using WebGL (I had some help from the three.js lib). All I did was define a canvas, add some lights, added a vertex buffer and used an already available arcball. Et voila: my simple model viewer was there. I am already assuming that IE will never implement WebGL. You'd think that Chrome and Firefox are to the rescue, but they're not there yet. So.. In order to run it on Windows RT, I have to create a fullblown app(!) (Unless someone can point a web 3D technique to me). So what are my options here? SlimDX? neh.. SharpDX? Still a lot of work.. I'm 48 hours further, and I have yet to see my first 3D canvas in a Windows Store App..
And then there's this toolbox. Geared towards games (gamebase.h) and still no simplified C# interface. It's a really great start, don't get me wrong, but it's still not as simple as it could be.I still have to: - Create the canvas in C++ - Parse the vertices in C# and then transfer to C++ - Compile for each individual platform
It's sad to see that Microsoft has no option for easily integrating 3D on Windows RT. And that while their rendering framework seems to be the best choice ever to do this!
Hope this gap will be filled up soon!
Disclaimer: There's always the possibility that I have grossly overlooked a certain technology
P.S: I believe that WPF initially had a solution for this with ViewPort3D. I haven't used this since it's not available on WinRT, so I thought: why bother. It seemed pretty much what I needed, though.