Common mistaken beliefs about the draft that create a good deal of misery and disappointment:
1. The purpose is to provide high impact players to fill immediate needs for the upcoming season. This rarely happens outside of the top 10-15 players taken.
2. The players rated the highest at a given position are going to be stars in the NFL. For example, this year's TE crop may not provide a single starter.
3. Players taken in the 2nd and 3rd rounds should always become good players in the NFL. The odds are less than 50%.
You're ideally trying to fill holes you've identified for the following season or two. At this point, though, that's the Patriots' entire roster other than cornerback, left tackle, maybe guard (depending on what happens with Thuney), center (assuming Andrews is healthy), and third down back. Maybe they find solutions internally but right now they're looking at medium-term needs at QB, TE, FB, WR, SWR, RT, EDGE, LB, S, and K, plus upgrades in line depth on both sides of the ball and maybe a luxury upgrade at running back. None of those positions have long-term stability with established players right now.
Like I said, you want to hope some of the solutions are on the roster (Stidham, Harry, Meyers, Cowart, Winovich, Cajuste, and Froholdt remain incomplete grades of greater or lesser promise and Johnson or Vitale could be long-term solutions to replace Develin). Some of these positions have been holes for a long time - no team is truly perfect - but the question marks at QB heighten every need.