In Ubuntu most anything you do outside of your own home directory requires you to become a superuser, in other words to become Root, or to gain root privileges which are all the same.
Now with being root you will have a greater responsibility to keep your system in a stable state but also a very high risk to break it. Root can do anything including breaking your OS to a state where you will have to re-install Ubuntu as the only option remaining for repair.
There are only rare conditions where creating directories outside of
/home/ may be needed. It certainly is not the way our understanding of the file system heirarchy is. In addition backups or a system reinstallation becomes harder with every single file residing outside of
So if you are a beginner to the Ubuntu world I strongly advise you to not create directories or files outside of your home directory unless you really really know that you badly need them to be there, and your are 100% certain that there is no other solution.