Orochimaru was evil evil, but his goals weren't, let's say... global. So he quickly became irrelevant.
Hidan was also evil, but sadly he was just an underdeveloped, minor character.
But knowing Kishi, if he gave the two I mentioned more panel time and story relevance, they would've ended up getting TnJ'd as well due to some sad childhood stories we haven't gotten to know yet.
You just need to deal with the fact that in Naruto, relevant villains will never be evil.