GNOME 3 is the best desktop UI I've ever used, and I've used MacOS 9 all the way to Sonoma, and Windows 3.1 all the way to 10. Critical point is that stock GNOME 3 is really terrible. Canonical has a plugin which provides an app launcher. This is the missing piece which makes GNOME 3 amazing. Using JavaScript will make developing bug-free software more difficult as the codebase scales though, it will make development slower and also slow down the code. That is absolutely a mistake. Not sure how much is JS currently; at least some it is. But I never have to look at the code because it just works. I'm on Ubuntu 22 LTS though, not sure about newer GNOME versions.
I will take JS over writing plugins in C any day of the week. Gnome devs felt the same way. This way, they can iterate faster on plugins and extending the compositor.
With TypeScript, I would agree with you. With JavaScript, you are trading one problem for another. And why not a pleasant, modern. C++ extension API. Because I've found with large JavaScript applications, it becomes harder and harder avoid bugs that would be avoided with a good indexer/linter during development. But with JavaScript, anything can be anything so there is not much to index.
PS Thunderbird also uses quite a lot of JavaScript. The calendar WebDAV sync is JS-based.
Curiously, I too prefer Gnome 3, but with at least one extension - hot edge to make moving to the bottom edge of the screen show the overview, and thus the launcher.
I'm curious if having JS makes the code more approachable for potential contributors or extension authors. And then if a project does "better" (measure utility to users? sustainability/longevity?) with more bugs but more engagement. Maybe that's just another way of asking "Cathedral or Bazaar?"
I'm on Fedora Workstation, latest version. Can confirm, current GNOME is still amazing and getting even better. But yes, this is all with the Dash-to-Dock extension.