Sure,you can code in a text editor, But a designer cant do precise and complex animations with a text editor.
Editing and creating animations are 50% of the value of Flash and that's why the IDE is still necessary to develop games, wether they are HTML5 or mobile ones. Yes there is Unity but Unity is 1/ more expensive than flash 2/ sucks at 2d asset creation.
So no, Flash isnt dead,by a long shot.
And the "dead" from the title refers to support from Adobe. The entire post is about how you can still target flash using OpenFL, haxe, etc.