No More Drinking
In Die Hard, McClane is physically hindered by his bare feet. In Die Hard with a Vengeance, his fragile physicality is summed up by the fact that he spends the film with a raging hangover. In fact, he seems to be on the verge of losing his whole career to alcoholism. For a movie with no family interactions to speak of, his stance as a drunk helped humanize McClane by illustrating his faults as a fella without actually spending any narrative time on his faults as a fella. Now he's drink-free and boring.