https://bloody-disgusting.com/editorials/3766201/fear-the-invisible-man-and-the-importance-of-public-domain-monsters/
QuoteI mean, if it wasn't for Night of the Living Dead accidentally entering the public domain, zombie movies would probably have become a Romero-specific specialty instead of an all-out genre.
This is not true. By definition, a genre is a category which includes similar patterns, structures, etc. Halloween has a copyright, but they still made Friday the 13th. The Exorcist has a copyright, but they still made The Conjuring. Dracula has a copyright, but they still made Mark of the Vampire.