I think he probably should have taken a corner angle to the sideline. I recall watching an NFL analyst probably a year or so ago (I think it may have been Brian Billick, former Ravens head coach) who was talking how our receivers were not helping Allen by continuing on with the dig instead of angling it into more of a corner route when there is a defender covering shallow. This particular play in NE was definitely underthrown regardless, but I remember seeing it often (his point) after he pointed it out. It’s a tough throw to judge to get over the shallow defender and if the receiver angles it into a corner route, it can be an easier target.
I’ll try to find the analysis clip.