I wonder if there might be an age thing about the skills of the likes of Smith and Fergie. When they were at their best they were older, already had the tactical knowledge and could work on the personal relationships. Plus they would have seen it all before with regard to troublesome players. Younger managers (and there are many in the game at a senior level, outside Scotland anyway) might be more imaginative and risk-takers on tactics but they don't necessarily yet have that extra skill that Smith and Fergie had.