That's why you won't see wide adoption of HTML5 in multimedia in the next 20 years. It's very complicated, unfinished, performance sucks. Even simple things like websockets are turned-off because of security reasons.
Some things won't work as an open standards. Doing games or MM in enviroment that should work on thin client and support gracefull degradation? That's madness.
Yes, first is overcomplication. You have one flash plugin that is same in every browser and works the same way every time. That's simple and effective solution. One interface, you make the change once, recompile and viola - you have a plugin for all browsers on the market, by utilizing some intermediate layer between browser and the plugin.
On the other have you have 10 browsers and you want to add eg. multimedia / movie support. That means every company will have to implement media player from scratch, beside everyone wants something different. Apple wants H.264 so website owners will pay them royalties for codec for playing movies, Google and Mozilla wants VP8 so they can have their business not affected by Apple's patents, etc.
So it ends up in implementing things that everyone wants (while VP8 or H.264 would do, for a start).
So before they can overcome their differences Adobe will implement H.264 in flash, use their already available streaming and DRM stack and... it's ready. 3-4 months and you have a working technology with 98% adoption rate.
Simple, one company decides, so they can push massive changes quickly and won't have to add "ideas" of 20 other "standarization body" members. Beside HTML5 is maybe 10-15 years behind flash, in multimedia. The gap will only get bigger. In recent MAX avant you could see game controllers support and fullscreen 3D racing apps, running on flash in full FPS, hardware acceleration support and so on. Meanwhile, mozilla can now play H.246 video without crashing the browser, but only play. Any additional functionality (like fullscreen, streaming, fast forward) is still missing!
Beside i think W3C is just wasting resources by trying to make HTML5 some half-baked copy of flash. It won't work... it's like trying to make flash a copy of HTML. Won't work.