Unfortunately, Application.Options.DefaultFilePath(WdDefaultFilePath.wdDocumentsPath), does not get or set the default documents path. It only gets you the current folder, usually the location of the document running the macro.
Here's a page from the Word MVP pages explaining the issue: How to retrieve Word's default Documents path or Pictures path setting Before you get your hopes up, the workaround on that page is no good for macOS, as most commands to use built-in dialogs are broken in Word for Mac VBA. I know, because I tried to program around the same problem a couple of months ago.
You can use AppleScript to get the user folder, then append the desired location to that in VBA. Sorry, I'm not an AppleScript guy, but there is helpful information on Stack Overflow.