We had several other languages once upon a time, but all were proprietary and most only worked through plugins. All were eventally removed from default installs in browsers due to awful security and mobile performance.
I was a Flash dev for some 10 years and I can count with one hand the number of third party libraries I regularly used.
I don't disagree about the security issues, mobile performance, and energy consumption though, but as a dev I preferred the experience of writing AS3 apps by a long shot.
