As I understand it, there was a period of about 35 years, maybe from Show Boat ca. 1928 to Camelot ca. 1962, when Broadway provided a lot of good songs that became hits, even when the shows were flops.
In the nearly fifty years since then, Broadway has produced few songs people remember, and many of those have been the product of Andrew Lloyd Weber. And throughout those fifty years, Sondheim has been considered the king of the Broadway hill.
So if Sondheim's opinion is worth quoting, why hasn't the public taken to his songs the way it took to his predecessors? I think that Sondheim is treated by the media as more important than he really is.