In a world of print media and books, 20 year copyright makes sense; it gives the media time to disperse through the population, saturate, have whatever impact it will on the culture, and throughout that time, the originator can profit.

In a world where distribution of a novel the size of War and Peace takes less than a one second download, there's no value beyond gatekeeping and exclusivity that publishers and platforms can provide, and those are arbitrary and artificially imposed, and entirely unnecessary.

Copyright is fundamentally a ceding of power by a society to individuals, granting them permission to claim sole ownership of their writings for a period of time, preventing other people and institutions from plagiarizing the work. We, society, cede the right to freely exchange information in deference to the creators of different media so they have the opportunity to profit from it.

The value of media is independent from the commercial activity which copyright protects. Someone attempting to claim authorship of public domain works might do it better, or maybe they make it worse.

There's no other purpose to copyright when the internet exists. We've seen nearly 4 decades of what this sort of system does; it allows those with lots of resources and lawyers to extort and exploit those without on technicalities and gotchas. It enriches and rewards middlemen assholes without concurrent return of value to society. It results in brainless reshashes and remakes and protected IP franchises into milquetoast formulaic omnislop. Any sort of actual creativity and variety gets suppressed or outcompeted or even legally squashed, even on the off chance that it might negatively impact sales. Books and films get destroyed as tax writeoffs. Artists get their music and writing and entire life work hoarded away by some massive multibillion dollar corporation, and sometimes even left to rot and fade away to dust, never to appear again.

The purpose of a system is what it does. Your idea of a copyright system has been tried, and it has failed. It's time to update to a system which works in the world which is.