I'm pretty sure the concept of petty or mechanical offenses for which you aren't entitled to a jury predates the Constitution, so I'm not sure I see the erosion.
Because judges have an abundance of faith in their judgment being balanced, and so presume themselves autocratic?
Historic violations don't really counter my point - even in the past the map was not the territory. Finding one non-erosion (by virtue of it never have been applied) doesn't change the rights that have eroded.