The problem is that with web being so many thing to so many people, there is not much everyone will agree on. A browser must be able to act as text document vie

The problem is that with web being so many thing to so many people, there is not much everyone will agree on. A browser must be able to act as text document viewer, graphic editor, game engine, chat, and with more of different usecases being pushed pushed into that pile, the more you want browser to be assembler of the web, otherwise you'll end up with a pile of incompatible "page structures", each required by some of those applications.