Interface-wise, a document is a static application and an application is just a dynamic document. In the flat 2d-world of computers they both are opposite ends

Interface-wise, a document is a static application and an application is just a dynamic document. In the flat 2d-world of computers they both are opposite ends of a spectrum and it's somewhat natural to move on this spectrum from one side to the other depending on your requirements and circumstances. From pov of the user on the other side the document is the result of a program, but you still open and interact with it from an application, thus we are back to the spectrum. Except with webstack we have better options to deliver a more content-optimized interface, leaving out some hoops, allowing to enhance the experience faster.