Not necessarily. If you're talking about the 2nd half of 2002 when Drew started to hit the skids after a strong start, you are right that defenses just played all cover 2 and neither Gilbride or Drew was able to adjust.
In 2003 though (his worst season), it was mostly blitz, blitz, blitz. Who can forget the Dallas game after the bye week, when they played 0 coverage on almost every play and we couldn't make them pay by making a single play downfield. Of course Moulds being hurt that year was a huge blow.