Our copyright terms need to be reasonable. They aren't reasonable right now. The term has been ratcheted up from the original 14 years with an option for a 14 year renewal to the ridiculous author's live plus 70 years, or 95 years from first publication/120 years from creation (which ever is shorter) for works for hire.
I'm all for keeping much of the current copyright regime around, including extending the term to some reasonable period after the author's lifetime. The terms need to be reasonable.
Copyright is granted by society. It should be based on give and take. Historically "normies" haven't paid any attention to it and the only parties who have had any say have been those who had a vested financial interest in increasing copyright terms. It has been a "take and take" relationship.
Preventing works from entering the public domain also has a "pulling up the ladder" effect. It prevents new works based upon older works from having economic value. The Walt Disney company's success and subsequent lobbying to extend copyright terms is a particularly galling example of this to me.
I'm not sure what you mean re: "...maybe forever (like indigenous culture)." Are you suggesting that making works that are derivative from indigenous cultures should be prohibited? At some level all of our stories are from the "indigenous culture" of all of humanity. There are no new stories under the sun.