To use it you have to adapt to those changes. Over the years Photoshop has often changed the way it does things. Nevertheless, VueScan showed up in the File>Import pop-out menu in Photoshop. No Import/Export folder as in past versions.
I found very few items in the CC2019 plugins folder. Thereafter it should (it did for me) show up in the Photoshop File>Import pop-out menu. Then open the Photoshop folder, navigate to the Plug-ins folder open this folder, and paste the file (Command-V) to the folder. The easiest way to move this to the Photoshop Plug-ins folder is to select it and copy it to the clipboard (Command-C). To find the plugin, right-click/Option-click on the application and select Show Package Contents inside you'll find only the Contents folder open this and you'll see the Plugins folder wherein you'll find the ugin file. The plugin does exist, but you have to install it manually, as you do the application itself. The latest one is the suggestion above that it installs a Photoshop plugin.
