The website tells the full story:
https://elm-lang.org/ © 2012-2021 Evan Czaplicki
https://elm-lang.org/ © 2012-2021 Evan Czaplicki
React's would say 2022 - https://github.com/facebook/react/releases
There's engineering effort happening behind the scenes on both projects, the releases have slowed, and big changes are coming to both Elm and React.
Dead means it's super stable. Stable is good.
Basically, if you build on Elm, you're living inside Evan's personal project.
There are upsides (Evan did a great job designing the language) and downsides (Evan's goal isn't being a maintainer, and he locked the ecosystem in such a way that many things can't be done without him).