That said, Ruffle ( https://ruffle.rs/ ) is keeping flash alive on the web, preserving the legacy of flash and enabling people to make new things like this! Newgrounds hosts a contest every year since the "death of flash" to see who can make the best new thing, (that's what this was made for, actually): https://www.newgrounds.com/bbs/topic/1523958
I think the last I heard from him was like a decade ago, so who knows, maybe he and his crew finally moved on to some other tool. But it definitely persisted in the animation industry long after the browser plugin got killed off. Adobe's still cranking out new versions every year, too, so it's not like you're stuck using ancient operating systems to run it.
While Adobe is still making animate Teen Titans Go! (a Spongebob-esque spinoff of the original show), as well as many other US animated shows past 2012, moved on to Toon Boom.
The WPH crew was pushing really hard on what could be done in the medium of a Flash cartoon delivered via a dialup modem, but it sure is hard to look at most of that animation now.