Well, but what would a layman justice do with all the legalese dutifully produced by his/her and others' clerks? To sit here with an open mouth would be undignified, to rubberstamp their output would not look too good either. Thus we either need a constitutional convention which would produce a radically simpler document not open to interpretation, or we are stuck with professional lawyers.
The Constitution IS a radically simple document. Compare it to just about any other nation's written Constitution.
What the author says is correct, except that we've spent a couple of centuries accumulating precedents that must all be weighed in making decisions.
While the Constitution is very simple, the accumulated precedents are anything but.