Think loading times are bad on script-heavy websites now? Wait until every web app uses its own mix of graphics, font and layout libraries, all compiled from C/C++ to WebAssembly and shipped in a 100MB blob. And rendered without any integration with accessibility technologies, and with basic things like copy and paste disabled to stop you "stealing" content. No thanks.
SVG 2 leaves the "painter model" behind (where z-order is determined by document order of the respective shape within its container) in favour of the z-index CSS property, so that you can address it in CSS (eg. `:selected { z-index: 1 }`). This makes it possible to describe things like interactive maps and DVD-like menus where when you click on a shape, the shape gets scaled or applied some other transform for highlighting.
However, I agree that SVG 2 leaves a bit to be desired (for example, level of detail properties). Also, animation of SVG in FF sucks compared to Chrome and Safari, or at least it used to 3 years ago. I wanted to teach my 12-year old how to make a simple browser game, but had to resort to hackish workarounds to make it run smoothly on top of using rAF etc., ruining my pedagogical ambitions.
I can relate to this, I use to work on a svg-heavy project in 2014 and I had the same kind of issues and I filed many bugs on FF bug tracker .
Fortunately, they've all been fixed by the mid of 2015. I don't work with svg so I don't know if everything works well now, but at least there were improvements.
CSS/SVG is used for websites.
Time will tell though.