Exactly! The type of stuff I built with Flex and Adobe Air was so great. I was able to solve so many problems that I just couldn't have (easily) without it. And for that brief moment when I could turn Flex code into iOS/Android apps? Awesome.
Yes, really. Adobe AIR has had supported for iOS and Android, practically since the beginning.
There was a big stink around Jobs "Letters from Flash" and all AIR applications were put on indefinite hold in the app store review queue with no explanation. Adobe stopped development of their iOS stuff. Then after a few months all the apps were approved, Adobe resumed development, and no one had a problem since.
What is FlexDeveloper? Do you mean Flex Builder [now Flash Builder]? It wasn't really killed, just abandoned, if there is a difference.
There is nothing today that offers a similar level of accessible crossplatform development like Adobe Air. Qt is the only thing that comes close.
Sadly Adobe decided to kill the Flash platform. I wrote a long rant here a couple of years back: https://medium.com/@Pier/why-im-finally-breaking-up-with-fla...