I think what Maggin was getting at in his introduction, by calling Kingdom Come the fully realized conclusion, is that Superman's super side, what might be equated with divine might, should be used as you say, YES. But not solving everyone's small problems should not have prevented him from acting as a man. Speaking out about the injustice and building goodwill for people who needed it could have been done in this story without acting as an Overgod.

(The subtext readers at the time would have known was that this was already happening at the time--Cesar Chavez created a union for field workers and his fasting and philosophy of nonviolent strikes put sympathy on their side--this story was definitely written in support of their struggle! But I suppose this falls into the realm of making the fictional world change too much.)