Titanfall 2's campaign tells the tale of Jack Cooper, a lowly rifleman for an interplanetary frontier militia that is fighting against the hegemonic control of the antagonistic IMC and its mercenaries. Cooper has just started down the path of his dream job—becoming one of the rarified pilots that gets to take control of a massive mech-like Titan. Following him through that entire career path would be too time-consuming for our purposes, though, so in short order Cooper finds himself thrust into the seat of Titan BT-7274 (BT, for short), forced to fill in for a pilot that is tragically cut down before his eyes.
As thrown-in-the-deep-end, fish-out-of-water tales go, it's about as cliché as it gets. The paper-thin plot driving things forward is a cookie-cutter tale involving a band of utterly amoral mercenaries working to secure an ultimate power source that, in turn, will be used to power the kind of planet-destroying weapon that you've doubtless seen as the Macguffin in countless sci-fi tales at this point.
The few mercenaries with speaking parts (who mostly serve as Titan-driving, level-ending bosses) are scenery-chewing, mustache-twirling villains down to the last person. While the game makes a perfunctory effort to grant them some meaningful character through bits of dialogue, none of these antagonists sticks around long enough for you to really feel any connection to them, good or bad. The random friendly militia members who aid you in your efforts are equally disposable, character-wise.