I've always liked the simple explanation offered up early on (probably by fandom, but after all these years I'm not sure) that there were simply different races of Klingons just as there are different races of humans. And if TNG had gone forward with that idea and simply shown a variety of Klingon types it would have worked just fine (as they seemed to try doing with Chang in TUC). Instead they chose the long practiced simple and cheap route of depicting every representative f an alien race as all exactly the same. That can work if we're seeing only one representative seen perhaps once (as happened with many Trek aliens), but it becomes a shtick wwhen we see more than one represtative and we see them often as was the case in TNG and DS9 and later ENT.