Cultural memory is powerful, only but in the context of Earth as we know it. There are some cultures here that have been bearing bad blood towards one another for centuries, purely by memory -- Arabs and Persians, for instance. 24th century Earth is so utterly different -- filled with nonhumans, for instance -- that I think most of it s culture would have been destroyed, both good and bad. To use your example of the Civil War soldier: those statues retain meaning because in our world, the soldiers who are memorialized have living descendants living in that place; their story continues. The problem with 24th century Earth is that it is SO different that the old stories are gone. The old stories had to do with material want and need, with inequality and conflict, etc. 24th century Earth is a magic place. Makes for sucky stories (see: early TNG ;-)) , but Sisko grew up there. Maybe it's a New Orleans thing...even in the magic 24th century Earth, there's still an African-American cultural memory that's survive all the aliens and magic. <shrug>