I actually don't see a problem with using a document renderer for applications, assuming it's actually treated that way. The document-rendering of a browser is

I actually don't see a problem with using a document renderer for applications, assuming it's actually treated that way. The document-rendering of a browser is lower-level than a UI toolkit, and that makes it more powerful in a lot of ways. But we need to be able to build abstractions on top of it to actually build UIs. I think react.js's approach (or something similar) is actually pretty good here. A lot of the problems we run into are people treating DOM nodes as if they were UI widgets, when in reality they are lower-level primitives for drawing and capturing input.