I agree but have hesitations at part of your last statement. It should not be just commercial interests that determine copyright, although they should play a part, and they have played a part in the recent extensions of copyright term. The advances to the author and the enormous cost involved in producing a book have warranted some increase in the term of copyright. No more literary tea party. The money people took over a while back.
The money people cannot seize a person’s creation, but they may entice. Creators volunteer ownership of their creation in the hopes of increased benefit. It’s a messy business, but not one that necessitates truncating the term, as if all must be up for grabs after 50, 60, 100 years. Every creator that wants their creation protected by copyright law is thereby obligated to defend his claim, so it is not as if it’s lifelong smooth sailing. It’s always a “sweat of your brow” thing, especially for those who lie, covet, cheat, and steal.