This. If I'm not mistaken, the system was meant to operate like a hybrid between patents and trademarks. Iirc, things weren't originally under copyright by default and you had to regularly renew your copyright in order to keep it. Most of the media in the public domain is a result of companies failing to properly claim or renew copyright before the laws were changed. My understanding is that the reason for this was because the intent was to protect you from having your IP stolen while it was profitable to you, but then release said IP into the public domain once it was no longer profitable (aka wasn't worth renewing copyright on).

Then corpos spent a lot of money rewriting the system and now practically everything even remotely creative is under copyright that's effectively indefinite.

"With 3 simple circles, I dominate the planet!" ~ERB's depiction of Walt Disney.