Things on the Linux GUI land are so messed up that we even got this.

I don't understand what you mean by this. This project is using a library provided by a major DE, if anything this shows the opposite of your point.

There aren’t distribution “sponsored” IDEs (like Visual Studio or Xcode)

Both GNOME and KDE have a text editor that supports LSP's and plugins, similar to VS Code. I also don't know anybody who still uses Visual Studio or Xcode, outside a specific situations where they're needed, which isn't a positive in my book.

userland API documentation

Linux has XDG Desktop Portals, protocols that all DEs and compositors can implement and can be used by any app.