While it relies on map luck, the encampments at 1/2 priced can be very beneficial if Carthage is around you. Then you can have 2 trade routes per city by building two districts and one of them is 1/2-priced. This can lead to a very productive empire, which helps all victory conditions.
Doesn't matter what age the world is in, if you get the civic, you can buy them.Archaeologists come around in the late Industrial Era. Correct me if I am wrong but I don't think you even get the option for monumentality that late in the game.