A lot of vlc functionality has been split off into separate packages - there’s one specifically for DVDs.
sudo pacman -S vlc-plugin-dvd
# or vlc-plugins-extra
# to see what plugins it pulls in: pacman -Si vlc-plugins-extra
sudo pacman -S vlc-plugins-extra
# or if you prefer, you can install all the plugins
sudo pacman -S vlc-plugins-all