I happen to like JavaScript but I agree about HTML, CSS, and the DOM. Actually I would like them to die. It doesn't take a PHD to see that we've moved beyond what the original platform was designed to do. It was designed for documents and styling those documents, but very little of what we do today is making documents. Webapps are king now and designing them means having to work around this outdated platform built for documents. It's so bad that now we require books such as JavaScript the Good Parts to explicitly tell us how to avoid these warts.
Instead of iterating further on HTML I think a new open platform should be built that specifically targets interactivity and building applications. Keep HTML for documents, what it was meant for, and begin focusing on something that can address the current needs of developers.
I would say a substantial amount of time is spent by most users using applications. For instance, Facebook might eat up more than 50% of some users time on the internet, which I think falls under the category of application. Or Youtube, Gmail, etc.
There may be a small minority or users who spend a lot of time reading documents (and I applaud them!), but most users are interacting with web applications.
Of the three examples you gave -- Facebook, YouTube, and Gmail -- you could make a good case that only Gmail is actually an application: it's a mail client that runs in the browser. YouTube is arguably almost as document-centric than Hacker News is; it's simply that the documents in question are built around embedded videos and their comments. Facebook is somewhere in the middle. It's accreted application-like qualities over the years, but at its core it's assembling a list of text and image items -- i.e., documents -- into a master timeline.
I'd submit that an awful lot of web sites that people spend time on have been made very JS-heavy and "application-y" despite being fundamentally document-driven. In part I'm sure this is due to the rise of native mobile applications -- have your server just use a JSON API and make your "web page" a JavaScript application that talks to it the same way your iOS and Android apps do. That development model has become the hammer web developers are using to hit an awful lot of things that maybe really aren't that nail-like.
I definitely spend more time using applications, and for the general population I'd bet even more. Webapps are what people are flocking too and that's where the industry is heading. Depending on your definition of application, arguably reddit, gmail, youtube, Stack Exchange, and Facebook are all webapps.
I'd argue that forum sites are primarily document based.
We've managed to emulate the functionality of a 1990s (or 80s!) dial up BBS and scale it up 100x (now instead of a thread having 200 replies it may have 20k replies), at and we are only needing a few thousand times the bandwidth and CPU power to do it!
Instead of iterating further on HTML I think a new open platform should be built that specifically targets interactivity and building applications. Keep HTML for documents, what it was meant for, and begin focusing on something that can address the current needs of developers.