As the name suggests, you must worry about the environment, whether it’s hurricanes, floods or volcanoes. You must consider climate change and the natural risks associated with choosing a place of residence. This extends to power supply. Your late-stage buildings must be driven primarily by fossil fuels, but you want to quickly move to renewable energy to avoid lasting damage to the environment. When you want to make your own changes, you can take technical upgrades like channels and railways.
Other additions? There is now a world congress where you will have a UN style, the ability to earn favors through alliances and even the opportunity to explain resolutions. New black death and WWI-based scenarios manage life and death in history. The expansion also upgrades the Spionage system as well as Culture and Science Victories. All in all, there is a lot to prevent Civ VI from getting old.