Regarding Android, yeah I get that it's optional (I actually didn't know that recent versions had made it mandatory). If you view Android as analogous to Windows though then I think it makes sense. There's lots of different devices running Android, some of which aren't even phones. My point is that, similar to desktop GPUs, you can choose a "lowest common denominator" API based on the maximum age of the physical devices that you want to support.
I don't see a problem with that approach. In fact it seems to be about the best you can hope for when it comes to hardware APIs in general (unless you're Apple and control all the hardware) since things are constantly being revised and redesigned.
Regarding Windows, what are you saying here? That Windows Store apps will be getting Win32 support in the near future because the sandbox will finally be able to accommodate it (but VK and GL will still be blocked)? Or that native (unsandboxed) Win32 apps will become sandboxed (and thus restricted) in the near future? (I suspect the former, which is neat but doesn't change anything regarding graphics APIs.)
I did learn a few new things here but am still left with the general impression that Vulkan has reasonably broad (and increasing) support while OpenGL ES 2.0 can target pretty much everything worth supporting (including most web browsers). (Of course I'd strongly prefer to use a more modern API than ES 2.0 if it's available.)
The difference is that desktops get updates, while on Android is more of wishful thinking targeting latest versions, unless one just targets Pixel and Samsung flagship devices.
Win32 sandboxing is orthogonal to the store.
UWP is not about the store, people keep mixing this up, as it unfortunely refers to multiple things across the Windows stack.
UWP is also known as WinRT, UAP, or just modern COM. And sandboxing UWP applications doesn't necessarly require delivery via the store. Any MSIX package will do.
What Microsoft is now doing (officially as of Reunion) is detaching all this tech from the kernel and have them as userspace APIs, across multiple Windows versions, and merging the UWP and Win32 stacks into one, hence Project Reunion.
Sandboxed Win32 applications don't need to be store only.
I don't see a problem with that approach. In fact it seems to be about the best you can hope for when it comes to hardware APIs in general (unless you're Apple and control all the hardware) since things are constantly being revised and redesigned.
Regarding Windows, what are you saying here? That Windows Store apps will be getting Win32 support in the near future because the sandbox will finally be able to accommodate it (but VK and GL will still be blocked)? Or that native (unsandboxed) Win32 apps will become sandboxed (and thus restricted) in the near future? (I suspect the former, which is neat but doesn't change anything regarding graphics APIs.)
I did learn a few new things here but am still left with the general impression that Vulkan has reasonably broad (and increasing) support while OpenGL ES 2.0 can target pretty much everything worth supporting (including most web browsers). (Of course I'd strongly prefer to use a more modern API than ES 2.0 if it's available.)