It seems it has been a couple of years since this topic was raised, and Sharepoint has changed a lot since then.
I have turned off the 'New Folder' option in Advanced Settings for all my SharePoint Document Libraries, however if a user is bringing a document from Onedrive, dragging and dropping folders into libraries or 'moving' files, there is still the ability to create a folder. This is really frustrating as I have to keep reminding staff to use the meta-data and views and not create folders. Their old Windows Explorer habits are hard to head off.
I really need another way of preventing folders from being created, preferably at a site collection level.
Thanks for the assist.