Totally true. Spending years fine-tuning the business logic and UIs made the eventual rewrites a lot cleaner and faster, having already iterated many times over the years and discovering what worked and what didn't. And learning TS after AS3 was easy enough. The real pain point was switching from a paradigm in which I owned the screen graph down to the pixel-level placement of each component, to a trying to wrangle similar behavior from a mix of DOM elements, relative/absolute positioning and arbitrary stuff drawn into canvases. Particularly for things like interactive Gantt charts and some of the really complicated visualization components that had been a relative pleasure to design and code in Flash. But yeah, it was much easier to learn a new language paradigm knowing exactly what I needed to implement, rather than having to devise the logic at the same time.

I think it was a very sound decision back in 2007 if you wanted to write once and deploy everywhere. In browser, and on the desktop for Windows and Mac. JS wasn't up to the task of complex SPAs or graphic visualizations yet (<canvas> didn't even exist), and the alternative would have been Java apps which relied on whatever runtime the user had installed. The fact that Flash/AIR could deploy with its own runtime or a browser plugin was huge. It allowed an independent coder like me to maintain multiple large pieces of software across multiple platforms at a time when it was almost unheard of to do that without a team.