> The Flash runtime itself is not particularly interesting, and in fact it’s full of undesirable problems. If you ignore the tooling of Flash, very little about it is appealing.

The runtime and the tooling go together. The reason why tooling doesn't exist for HTML5, SVG, and Javascript is it's just so damn complex and fiddly that it's impossible to paper-over and abstract with a robust authoring tool. Both sides of Flash were designed for the ease of this kind of development.

There hasn't been a good high-level authoring tool for HTML in decades and the situation is getting worse, not better.