Here is a short extract from Charles Hodge:
The only legitimate method of controverting a doctrine which purports to be founded on the Scriptures is the exegetical. If its advocates undertake to show that it is taught in the Bible, its opponents are bound to prove that the Bible, understood agreeably to the recognized laws of interpretation, does not teach it.
This method, comparatively speaking, is little relied upon, or resorted to by the adversaries of the Church doctrine concerning the satisfaction of Christ. Their main reliance is on objections of two classes: the one drawn from speculative or philosophical principles; the other from the sentiments or feelings.
Charles Hodge, Systematic Theology Vol. II, p. 527
Perhaps we could include under "speculative or philosophical" the claim that penal substitution is the product of a particular culture (in terms of doctrinal reflection) and is most appropriate to preach as part of the evangel if it resonates with that kind of culture today. Presumably if it doesn't resonate and speak to the culture you are trying to reach then it becomes a dormant idea.
We are approaching the atonement, on this understanding, not primarily exegetically but by selecting which aspect of the atonement we think best fits with the culture. Although it must be said that people who make this general argument are also known for their opposition to penal substitution.
However, you can be sure that if we approached the atonement asking "what has God said about it in his Word?" this situation would never arise. Try and select an appropriate "image," "model," or "metaphor" from Romans 3:21-26 for the culture you are seeking to bring good news to. It is impossible to do so since justification, redemption and propitiation (and hence penal substitution) are all present in the text and are bound up together.
If you preach the cross by expositing the text you will have to preach penal substitution.