It can't even be 1% of websites out there embracing this stuff. I'm guessing the biggest consumer for most of the new features in Chrome is probably Google web developers. There's quite a lot of things that only end up half implemented, too.
Although the RFC these days seems to just be a design spec doc for Google, I suspect you could carve it down to less than half of what it is and render 99.9% of websites out there just fine.