Dark Descent wasn't completely broken, at least on PC. Worked just fine for most people, that's why it has mostly positive reviews. 86% on Steam, while Fireteam has 78%. Fireteam has been out longer, so that isn't fair, but the same then goes for bugs. Fireteam had numerous bugs at launch, floating Aliens going through the floor, the game breaking bug of a stuck Alien that meant you had to restart the whole mission and waste our precious cards. And after a year of being out, when they added crossplay, it worked horribly at first, with so much lag and constant disconnects. And that's more than a year after launch. Now I know why they didn't have that at launch, since they weren't able to implement it well even later.
Both Dark Descent and Fireteam had a lot of bugs at launch and still have bugs. Dark Descent seems to have more problems on consoles for now unfortunately. But both games, on PC at least, were not completely broken on release and are both playable now for most users on PC at least.