Granted, Britt is a one-trick pony.
But he's able to pull that trick off time and again. Despite not having top-end speed, he consistently gains seperation on deep routes to stretch the defense. As a matter of fact, he did it again in yesterday's game. The primary reason for his low production is, unfortunately, poor production at the QB position - whether that be because of Nick Foles' inability to make the obviously play (see last year's Viking game), or Keenum's noodle arm.
Britt is doing his job.