I'm an author and I'd like to agree with you, however there's constitutional rights and then there's human nature.

If your constitution disallowed unlicensed sex, take a guess on which one would prevail - human nature or your constitution.

Also, read again why that clause is in the constitution - "to promote the Progress of Science and useful Arts". They clearly didn't have Disney in mind or the ever expanding "limited Times" that makes the public domain a legally obsolete concept.

I respectfully suspect you are misunderstanding history. First, the Copyright Clause permits, but does not mandate, certain forms of creative protection for a limited time.

Second, the clause itself states its goal. It was to encourage more creation, "preventing piracy" was a means to an end, not an end in itself.

And finally, there is good reason to think that regarding copyright in particular the target was never meant to be users at all, but other commercial grade publishers and competing authors. (It was prohibitively difficult in that era for an end user to make a copy of any substantial creative work so it likely wasn't even considered. I suspect, given some of Jefferson's comments in particular, that many of the Framers would have been against trying to apply copyright laws to end users had they realized it would eventually be an issue).