It is inconsistent. There are bad episodes ( "The Unnaturals" comes to mind). The power scaling is broken. But the emotional through-line— "With great power comes great responsibility" (told via DNA splicing)—is unshakeable.
Watching every episode of Ben 10 is an anthropological study of how a franchise grows up with its audience. You start with a bratty kid turning into Stinkfly to avoid homework. You end with a 16-year-old war veteran sacrificing his humanity to become a god-like alien (Alien X) to reboot the universe. ben 10 all episodes
When the original Ben 10 premiered on Cartoon Network in December 2005, it looked like a simple summer vacation story. A ten-year-old kid finds a watch that turns him into aliens. Simple, right? Wrong. It is inconsistent