I hate to say it but man, I miss Flash!! The websites, interactions and animations we were able to create in it 20 years ago..! There is still nothing that comes close to productivity and quality of output. I am disappointed that Adobe butchered Flash and wasn’t able to come up with modern and mobile friendly version. The war with Apple should have pushed them forward. Instead they gave up.
I’m only familiar with Flash as a user, not as developer. I’m curious, what did Flash have, that you can’t readily do with JS and Canvas? Be as broad or specific as you like.
Now you kind of have to think in code, and architect the site as a whole, there's less creative impulse, or simply messing around to find something cool. This interactive messing around has to be visual, ideas should be easily copy-pastable, etc.
Because it was easy to experiment with the whole interactive media, and you didn't really have to worry about differences in player (no touch, no mobile, player was independent of browser), you could create wild stuff in very short amount of time, and everyone could play with it in the same way.
I loved Flash. Sure, it wasn't accessible, wasn't SEO-friendly or searchable or linkable, and had no future in mobile, but it was a magical creative canvas quite unlike anything available now.