When America fixes copyright to be life of the author only, I will agree with your concerns.
Copyright is a limited exclusive grant in exchange for the expectation of having more works written/created/painted/drawn/designed. We should not just ratchet up the duration or scope of that exclusive grant without the expectation that we'll get more value out of it (more works) in the trade.
As you suggest, a time-based copyright term (such as the original Copyright Act term of 14 years with a single renewal) would preserve this incentive even for authors who expect they might die before the end of the term.
It doesn't take copyright to make a profit off of a work. the Criterion Collection includes Charade, which is out of copyright: https://www.criterion.com/films/603-charade
I'm sure the children of the author can come up with inventive ways of selling the work.
Art takes work. It makes sense to give the artist something concrete that can be sold so the artist has a chance of earning a living. If that right is passed down to the kids, at least the artist has something to pass along, just like other laborers.
Here's a deal: go write a book. If you are overjoyed to see people pirate it, I'll personally buy a copy. But I guarantee that you'll be heartbroken to see people steal.
Have some respect for people who work long and hard.