50 years ago was 1975. If copyright were limited to 50 years, we'd be looking at all of the Beatles works being in the public domain. We'd be midway though Led Zeppelin, and a lot of the best work from Pink Floyd and the Rolling Stones.
Also, Superman, Batman, and Spider-Man. Disney would still profit from the MCU films which they produced in the 2010's, but they couldn't stop you from releasing your own Batman vs Spider-Man story.
The Harry Potter books would still belong to JK Rowling, but the Narnia stories would be available for all.
The Godfather 1 and 2 would be in the public domain, as would be original Star Trek TV show, and we'd be coming up on Star Wars pretty soon.
If there were no copyright protection, these works wouldn't have been created. It is good that Paul McCartney and George Lucas and JK Rowling have profited from their creative output. It would be okay if they only profited for the first 50 years. Nobody is counting on revenue over half a century in the future when they create a work of art today.
This is our culture. It should belong to all of us.