This goes multiple ways

- An animation editor like Flash? Ther's still Animate

- A "multimedia" framework for standalone content? I would doubt there is a demand nowadays

- A browser-targeted/cross-platform animation editor? That would be nice.

For the latter, there were some tries already, even from Adobe. The problem is cross-browser compatibility and performance.

I'd really like to see something based on https://greensock.com/gsap/ They solved all the hard problems already, and its itself based on a Flash/ActionScript framework so terms and structures are familiar, eg. keyframe based tweens.