Truth does not change, but our view of truth changes. I used to view some things that I was taught in the bible as truth and later as I read it found those things as not true....
The example I can give is that many Christians if not most condoned slavery for many years. In fact the "Truth" was that the bible taught us we could have slaves as long as we treated them well... yet, now we view slavery as it is... wrong and evil... Truth never changed. Slavery was always wrong and evil, yet it was how people began to have their eyes opened to the truth that changed how we view slavery.
Again, truth never changed, but how we viewed it did. I am not the same person I was when I was firsts saved as Truth (being the Person of Jesus Christ) changed me from the inside out. Truth never change, but my mind as it is renewed, began to see Truth more clear.
Many seem to think that I am or that my friends are saying truth changes and that is not the "truth" at all... Truth is the Person of Jesus who now indwells us and by His Holy Spirit leads us and teaches us in His Truth. This means what was true for us yesterday may change today as the Holy Spirit reveals God's truth to us through Jesus.
I hope you understand that.
Now as far as "generational thing". I view some things like wearing ties. There was a time when no one wore ties to preach, then there was a time that every one wore ties to preach and not not all wear ties to preach... the tie really does not matter to the preaching. The truth (hopefully) is in the preaching and not in the tie.
I view modernism and post-modernism the same way. One may use the tools of either to express the truth of the Gospel. The truth is the Gospel and not modernism or postmodernism.