While the creative works from the 16th century can still be accessed and used by others, the data in some software programs from the 1990s is already inaccessible.
We have a massive system to regulate creativity. A massive system of lawyers regulating creativity as copyright law has expanded in unrecognizable forms, going from a regulation of publishing to a regulation of copying.
This does not mean that every copyright must prove its value initially. That would be a far too cumbersome system of control. But it does mean that every system or category of copyright or patent should prove its worth.
The real harm of term extension comes not from these famous works. The real harm is to the works that are not famous, not commercially exploited, and no longer available as a result.