In my experience there are times when building HTML CSS components is an anti-user pattern. I know HTML-CSS well, but is it the best experience for users? In some cases my answer is no.
In particular, with complex websites I believe that using graphic navigation is superior to other alternatives. When we want to navigate using {Google,Apple,Etc} maps we do not have a list of hierarchical menus. One does not navigate to the continents menu, then countries, then states, then cities, etc. You zoom out, you zoom in or you type a location. A user can quickly and easily go from a street view in NYC to a street view in Osaka.
I suspect that direct 3D graphics could be used in other situations, but have not had a chance to explore them. Low hanging fruit first.
(And yes, this is not a bug free system. Getting things to work across platforms, browsers, etc can be tedious. On the other hand most {iPhones, Android phones } seem to have strong graphics capabilities that make them able to handle a modicum of graphics. :-) )