That's some heavy duty creative editing you've done there, essentially snipping out the entire paragraph that ends with "The wide variety of delivery mechanisms, installation tools, and overall approaches to updates across the full breadth of applications makes it impossible to push all updates through this mechanism. As frustrating as this might be, it is also an important part of the ecosystem that we cannot just revisit for the installed base of software." Just a tad skewing the point on your part, don't you think?
I disagree. They could provide an AppX implementation for "legacy" apps that streamlined installation (like ClickOnce) and let devs convert to it but they chose not to provide that option. IMO they purposely chose this path in order to "encourage" the development of WinRT/Metro apps.