I didn't say there were "guarantees". I said the picks were "no brainers". There's a difference. After the fact, 20/20 hindsight, experts and fans are always right. But going into the draft, there are "no brainers".
For instance, who would be the better pick for EDGE/DE, Travon Walker, Aiden Hutchinson or Kavon Thibodeaux? How about CB? Sauce Gardner or Derek Stingley? WR? Drake London, Garrett Wilson, Chris Olave or Jameson Williams? Better pick at OT? Ikem Ekwanu, Evan Neal or Charles Cross? How many draftniks had those 12 going off in the first 12? Most? Many? Almost all? How many had 10 of them in the top 10? The differences between them may be fit, the defense or offense they're going to play on. But they were all "no brainers". Teams really can't go wrong taking any of them. How about the next 3? Jordan Davis, Kyle Hamilton and Kenyon Green? Davis and Hamilton were projected to go in the top 10. There's always a number of players, usually taken in the first round, usually taken in the upper half of the first round, that are "no brainers". And when some team throws an odd pick in there, the 'experts' and fans say, "WTF were they thinking?" Like I said before, "no brainers". QBs are the oddity. Overdrafted and therefore, more likely to fail.