If I may wax polemic...
Here's Adobe/Macromedia's fairly recent tech history:
* Use AS2, so much better than AS
* Use AS3, so much better than AS2 and soon to be the ES Standard. Whoops!
* Use our new 3D API, it sucks less than our non-3D API you hacked to kind of do 3D.
* Use our new, new unreleased incompatible 3D API, it sucks much less than our existing 3D API.
* Please continue to use our runtime because it has three virtual machines for three different languages, a 15 year old graphics engine we still haven't really modified to take advantage of modern GPUs, and an IDE that's a cruel joke.
And that's just Flash. They also spent two years hyping Atmosphere before abandoning it. They added a 3D API to Director, then ripped it out, then added another one, then basically left it without an update for five years.
So, basically, yes there's a use-case for Flash. Animated / interactive ads that run on a lot of platforms and custom video players that let you implement ads overlaid on video. Oh, and some casual games where you can ignore the fact Flash doesn't like to handle dynamic screen refresh rates.
Any new functionality Adobe bolts onto its carcass needs to be avoided like the plague.
That's really just about it.