You are missing a bunch of edge cases, and the law is all about edge cases.

An artist who works professionally has family members, family members who are dependent on them.

If they pass young, become popular just before they pass and their extremely popular works are now public domain. Their family sees nothing from their work, that is absolutely being commercialized ( publishing and creation generally spawns two seperate copyrights).

GP's not missing those edge cases; GP recognizes those edge cases are themselves a product of IP laws.

Those laws are effectively attempting to make information behave as physical objects, by giving them simulated "mass" through a rent-seeking structure. The case you describe is where this simulated physical substrate stops behaving like physical substrate, and choice was made to paper over that with extra rules, so that family can inherit and profit from IP of a dead creator, much like they would inherit physical products of a dead craftsman and profit from selling them.

It's a valid question whether or not this is taking things too far, just for the sake of making information conform to rules of markets for physical goods.

If copyright law is reduced to say, 20 years from the date of creation (PLENTY of time for the author to make money), then it's irrelevant if he dies young or lives until 100.

You seem to talk about fairness. Copyright law isn't supposed to be fair, it's supposed to benefit society. On one side you have the interest of the public to make use of already created work. On the other side is the financial incentive to create such work in the first place.

So the question to ask is whether the artist would have created the work and published it, even knowing that it isn't an insurance to their family in case of their early death.

Il not sure IP should be used as a life insurance, there’s already many public and private ideas tools for that.

Also it seems you assume inheritance is a good think. Most people do think the same on a personal level, however when we observes the effect on a society the outcome is concentration of wealth on a minority and barriers for wealth hand change === barriers for "American dream".

For writing many people only become popular after they are dead.

I heard this explained once as the art in some writing is explaining how people feel in a situation that is still too new for many to want to pay to have it illustrated to them. But once the newness has passed, and people understand or want to understand, then they enjoy reading about it.

As a personal example, I could enjoy movies about unrequited love before and long after I experienced it firsthand, but not during or for years after. People may not yet have settled feelings about an event until afterward, and not be willing to “pick at the scab”.

The other, more statistical explanation is that it just takes a lot of attempts to capture an idea or feeling and a longer window of time represents more opportunities to hit upon a winning formula. So it’s easier to capture a time and place afterward than during.

The weirdness there is tying it to someone's life.