Well... all I can say as a web designer.... there is ONE, SINGLE, line of code you can put into your website source that will fix you IE9 issues you are having with CSS. One line.... maybe 20-30 characters long. That's it.
I just offered one simple example. There are lots of things even IE9 seems to have trouble doing in the HTML5+CSS3+Javascript toolbox. And then again, the vast majority of IE users are not even on IE9. So "one line of code" won't fix the problem for ALL of them (and there are way more of "them" than there are of "us").
As far as the "vast majority" will never see your HTML5 site... I mean really... you are speaking of the folks using as far back as IE6... now, to be fair, you are right, that is a BIG chunk of people. But lets be realistic here... if I'm doing web design and hosting etc.... do you think those IE6 folks are my target audience? Should I waste my time and resources to appease them as well? They are an afterthought. Granted all of IE still makes up damn near 50% of internet browsers being used today... but in reality probably only a small handful of that 50% is my target audience.
They are older folks most of the time, and computer/internet illiterate folks who are using whatever browser came pre-installed on their machines when they bought them.
Congratulations. So to make the problem resolve favorable to the Apple-supporting answer you want to offer, you choose to just cut the head off of the big crowd to argue for the small minority? Do you do this for your clients if they say they want to reach as many people in the world as possible: "how about we ignore most of the people so that this will work for the smaller numbers with the latest & greatest browser technologies? Sure, only a small subset of the world will be able to see your offerings, but they are the "good" people, not old f*rts" (even if there are tons of those older people, many of which happen to have money to spend on consuming lots of products). And, by the way, we happen to sell an awful lot of product to the younger crowd who are using whatever browser came with their Windows computer, most of which is IE8 or earlier. There is not a HTML5-only option for them. Shall we just dump all those sales opportunities so that only the "good" prospects can see our offerings?
You know who those folks are being targeted by? Ever seen those shotty computer virus commercials? That's their target audience because those IE6 people are running such outdated materials and probably aren't even sure how to properly protect their computers from viruses.
Again, twisting the answer as if it's only IE6 users. Anyone can easily search for browser usage numbers to see that Safari & Chrome is still the tiny segment in a massively larger pool. For example:
http://en.wikipedia.org/wiki/File:Web_browser_usage_share_v2.svg
Do a little more searching and you can see IE broken out by versions. Even more interesting is converting what is often shown as percentages into numbers of people (many of which have some money in their pockets and are prospective buyers of many kinds of products & services). In general, the massive crowd that is IE is NOT using IE9, but instead versions 6-8. It's not just OLD people that don't know how to upgrade. And version 6-8 are pretty HTML5+CSS3+Javascript UNfriendly. Firefox has its own issues with HTML5 (again, anyone can do a search).
And again: even if we want to believe that Flash is nothing more than an alternative to Quicktime or Windows Media (a video codec), if we could wave a magic wand today and convert all Flash video everywhere to Apple's desired version of h.264 for HTML5, while we Apple users would immediately have iDevice access to all that video, the vast majority of the rest of the world would be locked out (couldn't see it at all). That's not just the IE6 users. Those trying to nail down a HTML5 standard can't even settle on ONE video codec standard. Flash video has been able to run on EVERYTHING (except iDevices, and only because Steve has chosen for his consumers rather than letting them choose for themselves) for what: nearly a decade now?
But Flash is much more than just a video codec. And it can do all kinds of stuff that HTML5 can't do. For example, what can be done with audio in HTML5 is a relative joke compared to what Flash can do with audio. We just went through a transition at my company hoping to embrace "the future" so that all of our interactive mixed media done in Flash could be replaced by HTML5+CSS+javascript. It couldn't be done. HTML5 just isn't as capable as Flash (YET). And embracing a pure HTML5 solution with a "die Flash die" mentality means the vast majority of the world (not just IE6) users would be locked out of being able to see our offerings (though the tiny group that is iDevice, Safari & Chrome, etc users could).
This new thing from Adobe is nice for what it is- at last a (somewhat) "for dummies" tool to help take advantage of a fair amount of what HTML5+CSS3+javascript can do today. However, note the simplicity of even the professional example. Where is the sound? Is moving objects around and bouncing letters the best that we can do as an example? Now compare that to the best people can do with Flash. HTML5 options and HTML5 tools have a long, LONG way to go to match the creative versatility of Flash options and Flash tools.
And still, even with these simple abilities to move boxes, bounce text, fade in and fade out, etc, put any of that on your business website as the sole way to make those things happen and only a tiny little group of people will be able to see them today. If you want the much, MUCH greater world to also see those effects, you'll have to ALSO create versions in something like Flash... which for business means double the work, double the time, double the cost, etc. And, oh yeah, you can do so much more with the Flash version than anything and everything you can do with this tool.
I realize it's easy for the "Apple is always right" crowd to go with the flow. But the practicalities of this are as inferred above. The magic wand conversion of all Flash to HTML5 would result in all that mixed media (much of which is not just ads or just video) being UNviewable to the vast majority of people connected to the web. If your website exists to help sell stuff, a pure conversion (jettison Flash, go with HTML5 only) means shrinking your target audience to a tiny fraction of people (mostly Apple & Chrome users) while sacrificing all kinds of niceties that Flash has long been able to do that HTML5 can't do yet.
HTML5 is the future. But that future is much further off than most here realize. While we Apple people are reasonably set up NOW for that future, most of the bigger world are far from it and won't immediately change their Internet hardware & software because "Steve says Flash is bad".
Personally, I don't love Flash or hate it. I'm in the business of helping companies sell their stuff to the world. Flash is a great tool for mixed media presentations that will run on just about everything out there including all Apple computing devices EXCEPT iDevices. HTML5 alternatives are relatively weak in comparison and definitely not an either (Flash) or (HTML5) alternative.
Bottom line: If business matters and one wants to offer mixed media presentations to iDevice owners too, the ONLY current and foreseeable future option is to create that media in BOTH (Flash & HTML5)... spending double the time & money to do so.