In my opinion, the series went from great humor in the first two seasons, to mediocre humor in the third-to-fifth seasons, with a brief return of humor in the sixth-to-eight seasons, and then finally to kind of boring in the ninth and tenth, and now it's completely lacking in quality. This is pretty common in prolonged series, from what I can tell. After a while they've done everything they can, and so they start scraping the bottom of the barrel for content, and then when that's gone, the series just starts falling apart. RvB is in that last phase. In my opinion, something new, fresh, and interesting, that won't go on and on and thereby succumb to story creep, is needed.

Vale,
Perseus