> Flash allowed to create web experience that is extremely difficult to do with modern technologies.
Like what exactly? I played/viewed a lot of Flash content back in the day, but I don't remember anything out of the ordinary that simply isn't possible/is extremely difficult today, want to jog my memory?
There was a period of time after Flash was deprecated and web technologies weren't ready to replace it, but I think we're beyond that today, unless I'm missing something essential Flash could do.
I recall only once seeing Flash being used to do something "out of the ordinary". It was a video at YouTube (back when it used Flash for its video player), which in the middle of the video "escaped" its container and exploded over the whole page filling it with an animation (playing over the rest of the page elements), going back to normal once the animation finished. That probably required special support from YouTube's flash player, and would never be allowed with its current use of the browser's built-in video player.
Definitely as possible today with a canvas covering the entire page but being transparent, probably exactly what they did with the <object> container for that trick too. Flash was constrained to the container, just like <canvas> is, and surely it wasn't actually "escaping" from that container, but the container was drawn over the entire window.
But, hard to know exactly how it was implemented without seeing the source, so I guess we'll never know.
From what I've heard elsewhere (never used it myself), it was the editor for creating flash content that nothing today compares to, that modern tools for creating content are the thing that's extremely difficult (to use) compared to the flash tooling.
I agree that the broad idea of client-side rendering is capable of much more than we currently see widely deployed in web technologies. However, I think citing Flash itself as an example is problematic because, while it was really good at some things, it was also flawed in many ways like being single-threaded, proprietary and having security issues.
Instead of citing a particular technology (whether Flash, HTML5, WebGPU, etc), which risks getting into the weeds of defending any shortcomings in one or the other, I'd rather propose that client-side rendering in general is still under-utilized and capable of so much more. I also think the under-appreciated elephant in the room is that Apple and Google have both been guilty of subtly manipulating web standards processes to nerf client-side applications. And they've been very clever about it. Sometimes proposing potentially exciting enhancements but later sabotaging them - always with some plausibly deniable cover, whether security, backward compatibility, accessibility, etc. Other times they'll 'embrace and extend' a new proposal - and then keep extending and extending until it either becomes practically unimplementable, unperformant, bloated or just collapses in committee under it's own gravity.
Bottom line: powerful, performant client-side applications securely delivered in real-time through the open web are bad for app store walled-garden models and businesses that rely on controlling centralized social media or gaming platforms. Advanced client-side technologies and standards aren't as good or widely deployed as they could be because powerful interests don't want them to be.
