Theology can go wrong is lots of ways, but two approaches in particular need to be avoided. The first is to claim that "At last we've got it." The second is to maintain that "We've always had it." The first is typical of liberal theologies -- the tendency to seek change in the light of new historical circumstances. The second is characteristic of conservative and orthodox theologies -- those that think universal truth is located somewhere in the past, so that out task is to reproduce it today in an appropriate form.
Illustrations abound. The Protestant Reformers played "At last we've got it" by recovering the biblical message they thought was obscured in Roman Catholic doctrine and practice. In the 20th century Walter Rauschenbusch played the game with his claim that the social gospel was the old gospel of Jesus recovered for the first time since the early centuries. Neo-orthodoxy (Karl Barth, Emil Brunner, and Reinhold Niebuhr assumed it, although his brother and my teacher H. Richard recognized that a new generation would arise to point out the errors of the current emphases, as they pointed out the errors of social gospel and others liberalisms. Later on liberation theologies (Latin American, black, feminist, Native American, womanist, gay and lesbian, e.g.) claimed to have newly discovered that that the Gospel is a word of this-worldly emancipation for the poor and oppressed, so that at last they have recovered the true Gospel of Scripture).
"We always had it" was the battle cry of 20th century Protestant fundamentalist perspectives that insisted on some fundamentals that must be in all theologies and neglected at the cost of losing eternal Gospel truth. Orthodoxies of all sorts (Roman Catholic, Eastern Orthodox, e. g.,) guard a body of divinely certified body of truth that they have have always possessed they must would guard against all revisionisms.
The point could be elaborated indefinitely, but let it be said that it is dangerous to play either game. Humility is called for on all sides unless some new absolutisms emerge (At last we've got it.) or some old one persist (We always had it.) Holding on to what is good in the past must be balanced by the need to be open to new insights and fresh adjustments to changing cultural settings.
Theologies are human creations, and it is idolatrous to absolutize any of them or to sanctify them by claiming divine authority for what they alone possess. We have this treasure in earthen vessels, and we must be ever vigilant about losing the distinction by committing the idolatry of claiming that our own mud pots are identical with the treasure itself and not merely carriers of some version of it. We can do this by our enthusiasm for something new that has at last got it or something old that has always had it.