That's how it was originally but over time the terms have been extended (largely due to advocacy from organizations that own large catalogs of copyrighted material). It's now tied to the life of the creator rather than the time since creation or publication.

Yep. It needs to be restored or even shortened beyond the original window.

IIRC, early copyright (say, during Mozart's time) required royalties to only be paid out for the first performance of a work.

And that is why some of these composers were so prolific - to keep up their payday, they had to crank out music instead of collecting on royalties of performances they were directly involved with.

Unthinkable today, really.