[0]: https://www.cnet.com/news/steve-jobs-letter-explaining-apple...
Some of the big name features of the new Web standards near the time of Flash's demise were able to replace many things that used to require Flash. You had <audio> and <video> to replace Flash to for embedding media. You had <canvas> to be able to draw arbitrary stuff with another ECMAScript known as JavaScript.
The Web replaced Flash.
The strength in flash was the ease of using the IDE(?) to create things like tweens and interactions in a way I can only compare to Visual Basic. Despite Actionscript and Javascript both being hypertalk-alike technologies (and now ECMAscript), the speed at which one could, say, create an interactive cartoon or cutscene in Flash is unmatched when compared to that of WebGL or Canvas. I venture to assert that this is because of the environment used to create these types of things was superior to typing raw code.
This entire argument, however, is based on me not being an expert in WebGL or Canvas, and not being aware of a Flash-comparable development environment to create projects for them other than a textual IDE.
The flash editor is still around, now they call it ‘Animate’. In addition to outputting Flash it can make video and ‘HTML5’ so you can use it like you always have but not worry about the user having a Flash Player.