On Catalina at least, variable-speed constant-pitch playback is still available, just hidden. Option-click on the fast-forward or rewind buttons to access it. It jumps in increments of 0.1x.
Thanks, I didn't know that! It doesn't let you go slower than 1x speed though, which was the useful thing. I used to use it to learn tunes by playing half speed.
macOS is full of things that randomly pop up if you click something while holding a button. That UX is so hilariously bad it makes features hard to find even when you already know they are there!
