"Well, considering that Irish voters were promised time and time again that the EU did not have tax competency and it has now acquired it by function creep"
The point surely is that Ireland were told what to do by Apple if they wanted headquarters there. All taxation is basically political; intelligent voters choose the MP whose party is likely to make them pay the least tax and allow stupid voters to get shafted. As soon as Ireland wanted access to a club which agrees certain taxes between its countries - a customs union - the Irish government has limits on the games it can play with tax as the other countries will have only so much tolerance for being exploited. It isn't function creep; it's inevitable.