That intellectual property is non exclusive doesn't change the inheritance problem.
If you consider it right to get value from the work of your family, and you consider that intellectual work (such as writing a book) to be valuable, then as an inheritor, you should get value from it. And since the way we give value to intellectual work is though copyright, then inheritors should inherit copyright.
If you think that copyright should not exceed lifetime, then the logical consequences would be one of:
- inheritance should be abolished
- intellectual work is less valuable than other forms of work
- intellectual property / copyright is not how intellectual work should be rewarded
There are arguments for abolishing inheritance, it is after all one of the greatest sources of inequality. Essentially, it means 100% inheritance tax in addition to all the work going into the public domain. Problematic in practice.
For the value of intellectual work, well, hard to argue against it on Hacker News without being a massive hypocrite.
And there are alternatives to copyright (i.e. artificial scarcity) for compensating intellectual work like there are alternatives to capitalism. Unfortunately, it often turns out poorly in practice. One suggestion is to have some kind of tax that is fairly distributed between authors in exchange for having their work in the public domain. Problem is: define "fairly".
Note that I am not saying that copyright should last long, you can make copyright 20 years, humans or corporate, inheritable. Simple, gets in the public domain sooner, fairer to older authors, already works for patents. Why insist on "lifetime"?