there rule set are kind of wonky and you have to remember a lot them when playing KO which still lead to less then steller mechanics and gameplay, they are definitely harder to play in a casual setting. also they are universally consider weak at the moment that even casual player are aware of it.
if you compare them to say Ironjawz, who are not exactly a top tier army, they have such easy to remember rules and mechanics and are considered fun to play that they even show up in tournament because people like playing them casually in that setting