Flash gaming was hugely successful largely because the authoring tools were excellent and truly accessible. WebGPU on the other hand is like one or two orders or magnitude less accessible (as it currently stands) than typical modern game dev, which is itself nothing compared to what Flash was back in the day. So on the one hand you have a tiny number of diehard tech nerds who can deliver some labor of love, and on the other hand you have gaming companies/studios, for whom the business case of shipping games constrained to low tens of MBs is largely nonexistent.
Flash still exists if you want it, it is just called Haxe now. Both major and a number of minor game development platforms can publish to the web. Checking itch.io there were 120 web based games uploaded within the past day (includes updates I assume). I would guess there are more now than ever before, but because there are more easily available commercial games for very little money on sale more people just get commercial games. Or download free games, which gives better controls than a browser. Although the games market in general is so much larger now that I'm not conviced there are fewer people interested in web games than previously. I suspect it is more a case of people who were personally interested in web games previously and aren't now thinking that it is no longer a thing.
Still a great and useful tool (tho over the years it became slower and slower with each release, just like any adobe product) but the export to html / air / openfl etc. are nowhere as good as the OG flash runtime of yore.
Useful for exporting movie and packaging assets / animations to then be consumed by a custom engine but not worth the effort that much when you have spine, etc. which are better supported and used in the industry.
Scaleform still seems to be used by some AAA studio (I'm always surprised to see it) but I can't imagine it they will continue to use it for long.
