For decades, Microsoft only made Visual C++ for Windows, and alternatives like DJGPP weren't very good. This isn't unreasonable, it's just how programming works when you target a platform. Visual C++ relies on Windows because it's a Windows program, and Xcode is written for MacOS, not for Java or Electron.
What is stopping you from writing an open source alternative to Xcode that runs on Linux?
you can code-sign with open-source tools. That's not the hard part. Signing with a certificate trusted by macOS , that's where there's no avoiding having to go to Apple.
What is stopping you from writing an open source alternative to Xcode that runs on Linux?