Oh, probably better to think of it as something along the lines of Left 4 Dead in terms of gameplay structure, then. You boot it up, run through a campaign, and it's done. You can play it again or move on to a different one. There's no Helldivers-style overworld campaign map or meaningfully intricate, dynamic campaign. Just a lot of alien killing. Your player level is the closest thing to progression, and it goes up so fast that you'll max out in a handful of campaign playthroughs (after which you can prestige if you want, but it's pointless as far as gameplay is concerned).