Personally i really like this DLC because it makes the mid game less monotonous. Usually the mid game is basically just expanding what you already built in the early game; until you have enough resources and tech to terraform.
This DLC adds underground mars in a special map. The transition is made in certain points on the map so it isn't accessible at the start. The underground has several precious resources that you can bring to the surface to help. It has different threats than usual. This DLC also requires to use rovers a lot which IMO is a plus because they are barely used in the normal map.
If you like surviving mars i think this DLC will add enough content for a new run.
If you didn't like surviving mars i don't think this DLC will change your opinion