> today we can do everything Flash did, and more, with HTML, and WebGL.

There's one big piece missing: we don't have an animation/gaming interface that's as easy and intuitive as Flash.

Flash didn't become ubiquitous because it was powerful, but because it was easy for any 13 year old to pick up and do something nice in a couple of days without reading any documentation or doing any course. Good luck getting anything to work in WebGL without any web programming experience.