Is this that "Living Constitution" I've been hearing about? Look around this thread and you'll find plenty of authority explicitly refuting this.
As mere fact-finders, I don't think they're necessarily any better than judges. Indeed, in some types of cases amateur juries are really not very good at fact-finding.
If a jury screws this up, it's the fault of the lawyer whose side they found against. But when it comes to simply determining whether a person is lying about where he was and what he saw, a jury is the best BS detector you're going to find.
Certainly the perception of jury nullification went downhill after the establishment of the Constitution, and especially after the Civil War. Opposition of laws imposed by an overseas monarch was seen rather more favorably than opposition of laws passed locally. At the time the Constitution was ratified, however, the ability of juries to act as a check on government was viewed as a good thing.
To be sure, jury nullification has some severe problems: