The church does not need to "become relevant" to the culture. Why not? Culture is not relevant. Why not? Examine history and notice the differences in each decade. In an attempt to be relevant, culture constantly changes; consequently, by endeavoring to become relevant, the current culture is always irrelevant. Culture follows patterns of confusion and continues to lower standards in order to accommodate sin; however, the consistency of GOD's Word is due to confidence. The bar has never been raised, but Jesus was raised from the dead to save us from ourselves. "Jesus Christ is the same yesterday and today and forever."
(Hebrews 13:8) -NASB
Therefore, GOD's Word is always relevant. Culture needs to catch up.