While I agree I think that part of the reason is that requirements are so much more complex these days. No one had to make a Flash animation responsive to different phone sizes and orientations.
Flash was a whole lot more than just video content back in the day. I have fond memories of applying wmode=transparent and having my Flash seamlessly fit into the rest of my page.
Yeah. Absolute ton of web interfaces in tech, to manage servers or VMs or storage arrays relied on flash interfaces. The transition off that was painful.
