Early on the show was actually pretty great, and had a level of humor that appealed to both kids and adults. Outside of the main shtick of the babies getting into perilous situations, the writing could be legitimately witty and clever, especially when the show would shift focus to the adults. Speaking of, the characters were also surprisingly well developed at first, both the babies and adults, and could even illicit a genuine emotional response. This is especially evident in the first few seasons.
Seasons 4 and 5, the pre-movie seasons, weren't so bad, but there was a notable decline in quality. The movie itself was surprisingly good and felt almost more like a return to the first few seasons, despite a few hiccups along the way.
Post-movie episodes felt another marked decline in quality, and the Kimi episodes basically brought the show to the floor. Not for Dil and Kimi themselves mind you, but they were a sign of the show moving away from its original tone, and towards a much more child-oriented one. By the time Kimi showed up, it was hard to enjoy the show as an adult anymore.