The original intent was good. You make something, you can legally ensure people can’t just copy your work and slap their name on it for profit. People could make creative works without fear of someone else ripping it away from them.
Then Disney just kept bribing politicians to extend it to a ridiculous degree so they wouldn’t lose Mickey to public domain until they moved his likeness into their trademark, which lives as long as it’s being used actively.
And then you have DMCA, where everyone is guilty until innocent and that whole can of worms, and DRM which is technically illegal to circumvent no matter how much time or what reason. Corporatization and the Internet turned that relatively simple and good ideas into an utter mess.