Here’s the thing: copyright term includes the life of the author plus a fixed period. So the works you and I nobodies produce will eventually become public domain after we die. HOWEVER, and this is just my underatanding of the laws and I’m definitely not a lawyer, not big name IPs because they are not registered under the human author, but a corporation that is both a person under the law and effectively immortal. So even if it’s two thousand years after George Lucas dies, Star Wars will still be copyrighted as long as Disney exists, and even if Disney dies, part of the process of corporate “death” is liquidation where they sell their IPs to the next asshole corporation.