It's also my understanding that book titles are not protected under trademark law, except for the title of a series, so The Lord of The Rings could be trademarked, but not The Notebook.
Anyway, characters can also be trademarked, so you could have a magic school in a movie that's not named Hogwarts and a little boy not named Potter etc. So, you can have similar stories using different charters, but your forced to produce an original work and not use or imply 'based on X'.
There are also rules that let you use others trademarks. So, you don't need to pay using a ford car in a movie, or having an older song on the radio.
We could also have a longer copyright that caps to 7 years after first sale or public performance.
My point is simply there is a lot more flexibility than total control forever, that still preserves artistic control in their lifetimes.
Further, some authors make their first book free on Amazon in electronic format in what amounts to advertising for their second book. As long as an author can 'make a living' being an author you need to demonstrate the need for additional revenue when they are not writing.
Only a tiny fraction of Music, TV shows, Books and movies get revenue over a very long time period.