I partly agree that the mechanics aren't that well worked out, but genocidal? That is just plain wrong. Genocide implies the deliberate massacre of an ethnicity. EU IV merely implies you culturally convert them, NOT ethnically. It would imply the Austrians start to speak French and become Cosmopolitaine, not that you murder the Austrians and have French ppl settle. That is a prepostorous idea cause it would imply they even have the demographic potential to do so

That said the whole system isn't that well worked out. I still like to see the divisions, I'm against grouping them together in se, I do wish for more 'policies' (in the broad sense, game events, modifiers, actual policies, etc) that might make the managing of minorities more interesting.
The whole idea that cultures could be 'converted' is itself somewhat retarded. In history it would be the exception, hardly the rule, plus it is only possible to pull of such feats for late 19th century nation-states. Early modern states lack all apparatus to do so.