Tree-sitter[0] came out of Atom performance optimization, I think, and that's a legacy that will live on a long time. Atom was in my view the closest thing to emacs out there, and it's sad to see that sort of user-empowerment not live on.
The emacs comparison definitely feels apt. Being able to simply use JavaScript and CSS to make changes to the editor made it feel so powerful. Maybe I just need to get around to learning elisp (or find an elisp-JavaScript binding…)
Lots of things came from Atom and it's development, so much I'd still consider it a success although the editor itself didn't live on. Tree-sitter, Electron, "text-editor as a browser app" all became popular ideas thanks to Atom. Is there more things coming from Atom that I'm missing?
[0]https://tree-sitter.github.io/tree-sitter/