I would be okay with just keeping it but limiting it severely. If you release music and you can't sell enough albums in 20 years, that's not societies problem. A lot of artists release albums every 1 - 3 years anyway, so they're always selling some records, or were before streaming became the way to "own" music. Most make their money off of concerts anyway.
For movies and shows, charge and increasing fee to renew the copyright. Eventually studios will give up certain movies. The older the movie the more you pay.
We could also just have some of the rights go away after X amount of years.
Maybe after so much time it's still not legal to copy the original work, but it is legal to make a cover song, or a derivative work using the same character.
At another point maybe it's no longer to illegal to copy for free, but it is still illegal to sell without permission.
I personally think we should have shorter limits for non-creator owners of copyright, and for creators it should be like 20 years or death whichever comes last. I also think compulsory licensing should exist for everything.
For movies and shows, charge and increasing fee to renew the copyright. Eventually studios will give up certain movies. The older the movie the more you pay.