In early levels, though, the lock-on targeting is pretty reliable - if something's in front of you in those first stages, after all, odds are you'll want to kill it. Later missions, however, force you to be more choosy. In one, for example, you need to blow up flying boulders before they smash into a prison where a bunch of your allies are being held. But when you try to lock onto those boulders, the game gets confused. Did you mean to lock onto a distant and inconsequential dragon, instead of that nearby hunk of mission-ending death-rock? The game thinks you did. And then it doesn't matter, because before you can do anything else, the level's boss will tackle you in midair, locking you into a one-on-one, tooth-and-nail duel that you can't escape from. And while you're distracted with that, the boulder crashes into the prison, killing your buddies and forcing you to start the battle over.
It's that kind of stuff that makes Lair frustrating - not difficult enemies, not devious challenges, but disorienting, unfair moments that make you shout, "that's bullshit!" at the screen. And that's not fun. It's not even challenging. It's just irritating. Add in that failure means you'll need to re-watch sizable chunks of the cinemas every time you restart a level (they only become skippable once the level finishes loading in the background), and you may have to muster some serious willpower to keep playing.