I remember that extension eating 3 GB of ram on my macbook because I had format-on-save on.
This plugin has been worked on and the issue could have been fixed by now. I rarely used VSCode for D because the language doesn're really need an IDE support like Java or Scala. But I do agree that for beginners and IDE support is important. I use vim with DCD: https://github.com/dlang-community/DCD
Just checked, the issue does not persist anymore.
VisualD if you're accustomed to Visual Studio classic it's pretty much the same.
D has a language server (LSP) you can use any IDE/editor that supports it