I didn't look into all those libraries he mentions but they seem to all require JavaScript knowledge. Which I wouldn't consider to be a low barrier. What was magical about Flash is the idea that, basically, if you could use MS Paint, you could create animations and put them online. Sure for more advanced games you would need to know Actionscript but you could just draw things and make them come to life. As a 12 year old kid with know programming knowledge that was incredibly empowering.
Not to say that newer HTML5 libraries aren't empowering but it's going to attract a different crowd.
I didn't look into all those libraries he mentions but they seem to all require JavaScript knowledge. Which I wouldn't consider to be a low barrier. What was magical about Flash is the idea that, basically, if you could use MS Paint, you could create animations and put them online. Sure for more advanced games you would need to know Actionscript but you could just draw things and make them come to life. As a 12 year old kid with know programming knowledge that was incredibly empowering.
Not to say that newer HTML5 libraries aren't empowering but it's going to attract a different crowd.
I suggest that you look at stencyl.com/ the whole Haxe ecosystem is really great.