But on the whole I think it made the web worse. Lots of sites had microscopic text that you couldn't enlarge, no bookmarking pages or maintaining state, no right click, never ending security holes, invisible to search, inaccessible to those with vision or hearing assistants. The list goes on and on.
For all these disadvantages, Flash had something modern webdev can only dream of: permanence. A Flash file from 2004 will work almost perfectly in Ruffle, 20 years later; video, audio, images, animation. A dynamic webpage or dataviz (the only interactive things made today) won't load on anything that doesn't have a full NodeJS server on a Virtualbox VM and untold number of npm dependencies.
Flash was not the problem, it was how people used it. Same as today.
It did have a certain (imo over hyped) DX that people had a fondness for & that the web wasn't catering to. This was good for users in that they got a lot of experiences they might not have otherwise had. But the experiences were 99% things the web could do, and the web experience as a user was better.
I'm not unsympathetic to the passing of the flash age (even given the treasonous un-webful proprietary closed app-like rot that it was). But I mostly wish we'd had more people writing competitive authoring tools for the web; we could have made a Flash timeline like editor, with svg and smil/svg Dom/css animations/css transitions. The DX was largely recreateable. I think it's somewhat over hyped, but I definitely see & am sorry that there haven't been successful popular web-targetting ways of doing similar.
I don't think the web is as impermanent as you project. Many sites will run fine from an archive. Sure, datavis sites not being able to get data you didn't fetch the first time is an issue, but flash dataviz's are just as liable to fetch data on the fly rather than bake it all in. Flash doesn't have an inherent advantage, more a happenstance one, and web archiving will take one far further than one might believe. Alas "save page as..." doesn't work; the promise of tech like http bundled seems high, but then the archival community groups went & did their own thing instead of joining up, and http bundles became another bland anti-Google rallying flag. Alas.
There haven't been a complete absence of Flash-like things, but on the web. There just wasn't much uptake. For all the people who swore Flash was the greatest, there weren't a lot of people willing to spend money or create a community around new attempts.
Flash was fun to dabble in, but it's unclear what value proposition similar tech has im todays world, besides being fun to mess around with (which I love but does not a market make).
As FruitLoops Studio is for Audio.
If you want to do the same you have to now know JavaScript, some library and some UI frontend.
Flash enabled you to add interactive to other than just a straight up black text on a white page.
You can't even copy text now on some SPA sites nor head back in browser history without being hijacked to their home page.
What we got isn't it either.