I think the key thing to keep in mind is that Flash gave you all of that from one vendor in a coherent, easy to make use of experience. We can certainly do the same things with JS and the technologies we have outside Flash, but it takes a lot of mental work to stitch it all together. You have to know so many frameworks. You have to know the type of frameworks you're looking for to do `x`. And then there's a lot of performance tuning because something done through canvas isn't as fast as something done with the DOM, etc. Flash was gross but useful.