“Some slight JS knowledge (rebranded as ActionScript)” is laughably inaccurate - the was a deep familiarity with AS and all its quirks to make a performant, durable, responsive GUI in Flash. There were layers to consider when shipping a self contained executable ala Adobe Air - there were other alternative IDEs and compilers apart from Flash proper - fonts, frames, bitmaps vs vector graphics, how audio and video embedding were handled - it was a complete platform, every bit as complex a battlefield as the browser wars.

Hand-waving AS3-driven app development in the 2010s as ‘some slight JS knowledge’ makes me doubt you were actually there. I was there, and that was not what was happening.