There is a best practice for SharePoint, “Say no to folders”. However, out-of-the-box, in libraries we have button “Create new folder” activated as default. From settings, we can disable but is can cause addition administration efforts. The problem is to remember when new libraries are newly created.
This feature disable Create new folder for existing and new coming libraries in a site. See pictures below:
Also recommended to use Feature called “Disable Explorer view” which is included in this solution
Install and use: