In short, the last six years has not changed the basic conclusion that the growth literature has taught us much less about how to get rich than it has about who is already rich. There is nothing particularly new in recent growth theory, but perhaps that is no surprise because there is remarkably little new in growth, either – the rich today are by and large those who were rich yesterday. That there might not be a holy grail of growth policy, however, is no reason for people of economic faith to stop looking, so no doubt the next six years will see another 13,000 articles on the subject to review.
That's fairly pessimistic, I think, but let's grant him his view. Let me quote Robert Lucas on why the next set of 13,000 articles, useless or not, must be written:
Is there some action a government of India could take that would lead the Indian economy to grow like Indonesia's or Egypt's? If so, what exactly? If not, what is it about the "nature of India" that makes it so? The consequences for human welfare involved in questions like these are simply staggering: once one starts to think about them, it is hard to think about anything else.