It's a hard genre to define. There's two main "sides" to the game: the first is an outpost building engine, where you design your outpost, deploy traps and guards, and generally do your best to set up defenses around an objective; the other "side" is a 1-2 player raid system where you raid outposts other people have created and try to get the objective and escape.
Not sure where exactly that falls in terms of genre; I haven't really encountered any other games like it to define a genre.
I probably would give it mainly the genres of sandbox, Base building, and parkour. Some others are jump n' run, fps, strategy and action.
But as @Kharel said it is pretty hard to give it a genre.