I knew someone would trot out the "rights" argument.
"to promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries". (US Constitution, Article I, Section 8, Clause 8)
Your statement doesn't include the "limited times" component. That is crucial to the balance of 1) the author, to motivate them (not guarantee!) to spend their time to write down ideas and stories and to be compensated for it, while 2) society at large can then grow from that and take it new directions after that.
If #2 doesn't happen, then whey did society at large agree to #1? The constitution is by "we the people" not "we the publishers."
Patents have the same terms as in the 1700's because it is good for business to be able to leverage the ideas of competitors (after limited times) to then invent/produce new goods that would not have been thought up and invented and created without this symbiotic relationship. Since it's a win-win for business, nobody wants to change the times.
Some exclusive time to make back the money invested, while after that society can use it to go down new paths and avenues that the author never dreamed of.
But, with mickey mouse, the publishers (not so much the authors) want to tip this scale over and have exclusive control - forever.
When will "we the people" say no to this abusive rebalance of the scales?
Interesting fact: When the original copyright term was set to 28 years, guess how long it took for information to double in the world? 28 years. Now, it's doubling every 13 months. I would argue that copyright term should be tied to the rate of information doubling.
The most basic solution that I can suggest, to avoid this whole "extension" mess, is to not print in a book what year it was published (which leaves the date it enters the public domain up for after-the-fact changes) to have works indicate the date it was first published and what the date will be when it enters the public domain, based on the publish date at that time. Then, it can't be extended. it's already determined at the first publish time. A person can pick up a book and know if it is in the public domain or not. Today, legally, it is such a mess to try and determine if a book is in the public domain, that nobody even tries if it is after 1978 (~45 years ago)