I too tried to use a notebook with to-dos as a shopping list app, but it's very limited, it turns Joplin into a very basic list app : no dual list (item list with all items → shopping list with items to buy), no way to group items by categories (fruits, dairy, hygien, ...). I wouldn't call that a shopping list app.
I ended up doing something more elaborate (see https://discourse.joplinapp.org/t/joplin-as-a-shopping-list/32285), but I still think there's some space for improvement.