I truly hope that we have learned our lesson from Flash and choose formats like SVG (human readable and an open standard) from now on for things like animations and games.
At best, there will be crippled, lossy exports -- lossy because vendors chasing lock-in and network effects don't want to make it easy for customers to leave.
I've cited the demise of Opcode and Studio Vision in the past when making this argument, but that's niche. The Death of Flash brings down the point with greater weight.
At least with a flash game, you can often just download the .swf file and run it however you like.
With HTML-based stuff, you're often reliant on a server being up. Authoring tools are also just not what they were with flash - the sheer number of quality vector-based games and animations has dropped like a rock. I'm not sure if this is something Adobe will resolve eventually, but at the moment it's just kinda sad.
When anything is dynamically generated things get iffy, though. It’s one of the big problems both Google and services like the Wayback Machine and Pinboard have had with searching and preserving content.
Of course gaming as a whole has also evolved, so it’s less likely you’d ever get a purely single player game in the first place, and who knows if the game will even load in 10 years if it can’t connect to the server to see if you’re registered or not.
Not for AJAX requests they don't!
For all its faults, whether a Flash game worked or not came down to "did you install the plugin?".
And the fact is that most of the open technologies take years in order to become as full-featured as the closed-source ones. By that time the trend that artists were following is out of fashion.
By the way - if we think about it. Are there yet any actual tools that allow you to program SVGs as easily as you could once program Flash? I understand it's technically possible to compile from Flash sources to SVG, but are there actual tools yet?
There's Synfig Studio that's open source and supports SVG export: https://www.synfig.org/
Also it would technically be possible for someone to write a WebAssembly flash player. Although I don't know if anyone will feel particularly motivated to.
But that's hardly unique to Adobe. Any document format that allows (arbitrary) other things to be embedded is subject to that. A Word document with other things embedded in it is no different. (Just like correctly rendering or editing an OpenDocument file would require you to implement half of SVG and MathML – while they're open specifications it doesn't necessarily mean you have an implementation at hand you can use.)
https://bugzilla.mozilla.org/describecomponents.cgi?product=...
Why not do it yourself? Archive your favorite games. Datahoarding is a fun hobby that can help others.