I've trying to do this for a while and it just doesn't want to work. It installs the plugin, it shows the plugin, but upon opening a new Vim instance it just doesn't load the plugin. I think it might be something to do with macOS (I'm using Catalina) but I'm pretty sure that's not the case.
Here are the screenshots of the installed plugin:
And there is the picture of a new Vim instance with a non working plugin: