Flash Pro != Flash Plugin
It's worth noting that Flash Professional/Animate is a content authoring tool and not the Flash Player browser plugin.
Granted, the browser plugin is likely exactly what comments here describe, however my recollection of the authoring tool was as a great graphics package with a powerful language that allowed for rapid prototyping and cross platform support. (in-application code editing was a pig, but there were some great editors available)
I've not used Flash Pro in many years, but if Adobe could take the authoring tool (with support for ActionScript3) and shift the primary export to HTML5, no-plugins required, I'd certainly consider using it again over plain old javascript. It'd then be as safe as anything else on the internet...
"Flash" is undeniably a dirty word, as can be seen from some of the comments, it's not surprising they've decided to phase it out.