This gets to my distinction between "Principles" and "Values." Principles, such as "all men are created equal," are timeless and should not change. However, how we value that principle will evolve along with our culture. A value being a principle with a judgment applied to it.

For us to ignore changes in our culture, technology, etc that evolve over time and cling to values assessed to these principles nearly 250 years ago would be dangerous. That said, to abandon principles that we no longer understand (such as the right to bear arms) are equally dangerous. An armed, informed populace that is free to peaceably assemble is crucial to deterring the three branches of government from ganging up on us.

The entire mix works. Preserve the principles, but let the values flex to retain relevance.