Your download should now begin in the form of a zip. Select Visual Studio Code from the four options and click the 'Download for Mac' button. You can still get MonoDevelop for Mac, Windows and Linux, though the Mac download is now Visual Studio for Mac, and on Windows you have to build it from source.
When Microsoft acquired Xamarin in 2016, Xamarin Studio became a Mac-only IDE and was renamed Visual Studio for Mac.
In some ways it's unfortunate that the Visual Studio Code Mac, Windows, and Linux versions perform to such a similar degree, because it highlights the shortcomings of using the original Visual Studio on Mac.
On the other hand, Visual Studio Code for Mac (which is a totally different app to Visual Studio) has a generally positive reputation.
