There's definitely more to Exoterra than just the initial race and exploration. Currently in the free build you can change Kaitlin's body type, watch her masturbate, and unlock dildos and butt plugs by winning the race.
Additionally, the Patreon release has more content and is in active development, with new features, and plotline being added regularly. Features that include multiple races, fuckable characters and a drivable BFRV.