I was well into the final part of "Getting In" (a section on church membership), when I realized I was reproducing material that would likely appear in the introductory chapter. So here's a slight detour.
The first chapter: "The Myth of the Ideal Church"
1.1 The Good Old Days
We humans tend to idolize the past. The idea of some past "Golden Age" in the history of our particular people is all too common in different cultures. A society remembers the good of that golden day and forgets the bad. It pictures the courageous with more courage than they probably had, the wise with more wisdom than they may have had, and the strong as the likes of an Achilles or Hercules. Oh, if we could only get back to the good old days. 
To be sure, there are exceptions. The spirit of the late 1800s was to see human culture at its peak, with visions of utopia dancing in its head. Those were the days of Charles Darwin's evolution and of Karl Marx's classless society.  Whatever the value of Darwin's theory might be scientifically, it is no surprise to see it arise when it did, for those were days when progress seemed the way of history. Until 9-11 and the economic crisis this last decade, American society was perhaps on a similar trajectory to see the world only getting better and better as the days go by. Probably still, we expect the cell phones to do more and more things, the internet to replace the need for libraries and books, and robots eventually to be smarter than we are. 
It is perhaps sobering to realize that these same dynamics seem to apply all too well to the way Christians look at things. When we perceive ourselves to be in power, we might wield that power to try to force the world to be like us or our Christian group.  When we are drastically out of power and we seem on the verge of elimination or destruction, we tend to think apocalyptically, thinking that God will break into the world at any moment and destroy all our enemies in one swoop. But in milder times, we might look back to the good old days, when people were more spiritual, more filled with the Spirit. We yearn for "revival," a re-awakening to life, like the revival we had back at such and such a time.
In such times we might tell ourselves the story of the "dying of the light." We tell of how the first generation of our group was so full of the Spirit that they did all the things we should be doing without anyone needing to urge them to do them.  Then the second generation came along and institutionalized the experiences of their parents without experiencing them for themselves.  Finally, the third generation went "liberal." Perhaps they abandoned the original vision of the group altogether or watered it down with little personal investment in it. Those who tell this story are often in the fourth generation or later, who are far enough away from the first generation not to remember its faults and yet aware enough of its own failings to yearn for a better day.
There is some truth to this cycle, although we suspect the second and third generation might often tell the story a little differently than the fourth and fifth. The second generation might tell of the excesses of their parents' generation because they remember them. For example, they might remember that the same "hero" who founded that seminary was also a notorious racist or used to beat his children senseless. Or they might remember that the same woman whose writings said such powerful things was quite bizarre in other ways. Or they might remember that the great thinker also had a lifelong affair with his secretary. Similarly, the third generation might say they had enough distance from the the first generation to see where it had gone to extremes. 
Our point is not to deny the strengths of founding generations or to claim that no generation is better or worse than any other. The point is to stop and take a look at ourselves as we look back at the early church. It is to realize our human tendencies and the forces at work on our thinking so that we can see the past more clearly. It is no surprise that we hear so much rhetoric about "getting back" to the New Testament church or even "back to the Bible." The tendency is as predictable as it is a warning that we are probably looking at the early church through rose-colored glasses.
When we speak of "the myth of the ideal church," we are talking about this idea we often have of the "pure" church and our tendency to equate it with the early church of Acts and the New Testament. We are calling it a myth not only because it seems to be a skewed sense of the situation but also because it is a typical kind of story a group tells itself to express its sense of identity and its vision of the world. Perhaps in this case the vision is largely correct. But until we recognize how much of it is ours, rather than the Bible's, we run the risk of getting off track without even realizing it.
 Perhaps this spirit is most driven in days when one is moderately disatisfied and disempowered with the way things are going. The apocalyptic approach is perhaps more typical of desperate times, where things seem so bad that you look to a sudden judgment or end to history as we have known it.
 Not to mention the philosopher G. W. F. Hegel, whose sense of inevitable progress bolstered Marx's sense of societal evolution.
 Although this optimism in relation to technology does not seem to apply to our sense of human future. We do not currently have a sense that humanity is getting better and better.
 It is no surprise that "post-millennialism," a view that often sees us as Christians preparing the way for the coming kingdom of God, dominated during the centuries when Christianity was largely in control of Western culture.
 I take this phrase from James Burtchaell's 1998 book about the seemingly inevitable secularization of American universities over time: The Dying of the Light: The Disengagement of Colleges and Universities from Their Christian Churches (Grand Rapids: Eerdmans, 1998).
 When we get in this "looking back" mode, institutionalization becomes a dirty word, as it is currently in so many circles.
 We are not suggesting that all of our heroes have dirt on them if we dig hard enough. I personally believe that there are genuinely holy Christians who are blameless in God's eyes. Indeed, I would personally affirm that we can all be truly Christ-like through God's power. All we are suggesting here is that our heroes were real people, not demigods.