It still works like a charm. If by ‘new’, you mean Mx9, yes, major change since Mx8. No more Calypso.
But since Mx9: no, there are no breaking changes.
VSCode is not even obligatory. You can use any text-editor. You can even use Mendix Studio Pro → Styling
As soon as you save any change you have made, using any text-editor, MxStudio parses this to the new styling and it becomes visible immediately.
Do make sure (which you probably have done several times already) that you have the correct folder and file(s) open in your text-editor.
the 2 main reasons why custom CSS styling are not processed on the screens are:
Good luck with it,