Hide form "Add new user" in wp-admin/user-new.php

Good Morning

I would hide or become invisible in the form “Add new user” within wp-admin / user-new.php part of adding new user leaving only the option to add an existing user.

One option is to modify the stylesheet by adding the following sentence to hide such sub form:

form # createuser {
     display: none;
}

The problem with this solution is that I have more than 15 active topics usandonse in different sites and therefore the file to be modified is different or which does not correspond. Besides potential problems when an update of issues is made, reintroducing this custom CSS to hide that option.

Would there be a simpler way to do this? You could maybe play the file “functions.php” of each active topics? Any other alternatives?

Thank you very much in advance.