While you can delete stock folders such as
Public and so on, they'll still appear in the sidebar of your file explorer.
The good news is that they're pretty easy to disable.
Referring to the xdg-user-dirs manual shows us that there is a configuration file of "well known" user directories that lives at
$HOME/.config/user-dirs.dirs by default
Simply deleting the various entries inside might break a number of things but if you look closely, you'll spot that changing a directory to point to your home directory will disable it
> cat $HOME/.config/user-dirs.dirs
XDG_TEMPLATES_DIR="$HOME" # templates is now disabled
This should cause the Templates folder to disappear from the sidebar of Nautilus although you might need to restart first.