Style by itself cannot be copyrighted as the law currently stands. Therefore not illegal, regardless if said style originator has been dead many centuries or is currently living. To make it illegal would require drastic changes both legal and political, and even then no guarantee you'd get the desired results in this case. Be careful what you wish for ...

https://reason.com/2023/01/19/dont-let-disney-monopolize-a-i-generated-art/