Amusingly, this is actually a situation where a lack of studio interference caused the problem. They had offered more episodes, which Dan and Dave declined to make.

Obviously, the show was on the decline since season 5, but the precipitous drop in quality in the final season was because D&D were rushing to finish it all off. An extra season being forced on them by the studio might have allowed the final 2 seasons to continue the gradual decline in quality instead of jumping off a cliff like it did.