I don't know if he's one of the biggest busts in history but reality is, seeing your first round pick not hit the ground running and instead look like a long term development project is disappointing. Teams count on their first rounders making some impact. The Cowboys ignored FA at DT because they were banking on Smith making an impact.
It's just disappointing at this point. Now hopefully with more game reps he gets better. But right now, he looks sluggish off the line, seems easily pushed around, etc.