Dunno that much about Nicktoons since most of them are pretty shitty to begin with, but Nick's supposed flagship Avatar got such terrible DVDs that the community had to do some absolutely ridiculous work to get them into a usable state - a decade after they were released. Only then did Nick finally get off its ass and release a Blu-ray set with the worst issues fixed (but which still has problems), and that was after doing a boxed DVD set with the same horrible-quality discs from a decade ago.
Now if you compare CN to Disney, it's obvious the former isn't so bad after all. Disney is just fucking terrible with DVD releases, even shows like Kim Possible which would sell like fucking hotcakes are not fully on DVD. Later series get absolutely NOTHING unless your name is Alex Hirsch (and even then you have to beg them).
(Ironically, WB has done a million times better with physical media than both, despite being part of the same company as CN. Though even WB has issues of its own.)