A reviewer to Sanford Levinson's book critiquing the Constitution writes:
I can only thank the good Lord that we have Sanford Levinson to correct the fools who thought that they had a workable document that only got us through a bit under 250 years. Too bad he wasn't around back then--I'm sure that the Founding Fathers would have sat up and taken notice of his clearly superior genius.
I can't speak for Levinson, but yes, I could totally write a better constitution. Know why? I have 250 more years of historical knowledge and contemporary context with which to ensure it's applicable to modern times. For instance: I could write a way clearer 2nd amendment, and I'd limit judicial terms to 12 years, and I'd make the electoral college go bye-bye. Editing is easier than writing. Someone can give me a document I lack the capacity to even understand and, by changing a few commas, correcting a run-on sentence, and adding a footnote, I could make it better. You don't have to be smarter than the Founding Fathers to approve on their model.
That said, my wise, forward-thinking commenters are surely right that there's absolutely no way our current moment of hyper-polarization and cable news could create a better document. Of note here is that the Constitution was created by a group of highly select elites with basically similar class interests (though wide philosophical disagreements) and very little public input. For better or worse -- and in no small part because of the Constitution -- things are more democratic these days, and no such construction process could be replicated and then deemed legitimate. When you open the process up, it turns out women, and minorities, and the poor, have somewhat different demands, and that makes life unwieldy. Constitutions need to be wieldy.