Several points of contention...
First the narrative fallacy: because Watson was a successful college quarterback at a successful program, he is heir apparent to Tebow, VY, Manziel, etc., doomed to failure in the NFL. (RG3 doesn't even fit your archetype, as Baylor was hardly a national power when he was there.) Bottom line, these comparisons are lazy. His style of play, other than his mobility, is quite different from any of your examples. Furthermore, very few "experts" are predicting that he will be the first pick, or even the first quarterback selected. I would then ask, should teams avoid drafting a big qb, strong armed, pocket passer from a non-"top", power 5 school because Ryan Leaf, Ryan Mallet, Tyler Bray didn't pan out in the NFL? Whatever method you use for sorting past and present college quarterbacks, there will be NFL studs and busts in each cluster.
Next, your assertion that the majority of quarterbacks's do not come from successful programs, while superficially true, is based on spurious reasoning. There are maybe 10 or 15 "top" programs (defined as some combination of past/present on-field success, revenue generation, brand power, recruiting, NFL alum's, etc.) out of 128 FBS programs and 124 FCS programs. 7 of 32 "primary" starting qb's in the NFL last year came from "top" programs; 17 of 32 came from non-"top" power 5 programs; 5 of 32 came from FBS non power 5 programs; 3 of 32 came from non-FBS programs. (You could even make the argument that some programs I place in the power 5, non-"top" bin, such as TA&M, Oregon are "top programs. Where Clemson falls is debatable but I would include them in the "top" bin given the combination of past/recent success, brand, recruiting/NFL success.)
In descending order: 124 FCS programs, 59 non-power 5 FBS programs, 54 non-"top" power 5 programs (including independents), and 15 or so "top" programs. Therefore, we can determine the number current starting NFL quarterbacks produced per pool. It is quite clear from this data that, while top programs don't produce the largest gross number of starting NFL qb's, they are most efficient in doing so. We can debate what constitutes "great".
CSQB = Current Starting QB
3/124 (0.024 CSQB/Program): FCS programs
5/59 (0.085 CSQB/Program): non-power 5 FBS programs
17/54 (0.315 CSQB/Program): non-"top" power 5 programs
7/15 (0.467 CSQB/Program): "top" programs
QB's from "top programs"
Tom Brady, Michigan; Jameis Winston, FSU; Matt Stafford; UGA; Carson Palmer, USC; Cam Newton, Auburn; Sam Bradford, Oklahoma; Cody Kessler, USC
QB's from power 5, non-"top" programs
Russell Wilson, NCSU/Wisonsin; Marcus Mariota, Oregon; Matt Ryan, BC; Aaron Rodgers, Cal; Andrew Luck, Stanford, Brock Osweiler, ASU; Drew Brees, Purdue; Andy Dalton, TCU; Philip Rivers, NCSU; Tyrod Taylor, VT; Jared Goff, Cal; Kirk Cousins, MSU; Eli Manning, Ole Miss; Ryan Tannehill, TA&M; Jay Cutler, Vanderbilt; Trevor Siemian, Northwestern; Dak Prescott, Mississippi State
QB's from FBS, non-power 5
Derek Carr, Fresno State; Blake Bortles, UCF; Alex Smith, Utah (MWC when he played), Colin Kaepernick, Nevada; Ben Roethlisberger, Miami (OH)
Joe Flacco, Delaware; Carson Wentz, NDSU, Ryan Fitzpatrick, Hahvahd
"What they fail to understand is that you don't take wins with you, or stats, or trophies, what you take to the next level is arm talent, accuracy, anticipation, mobility, reading coverages none of that has to do with how many games you win in college."
I would argue that all of these traits influence how many games you win in college. If a quarterback cannot translate these traits to success at the college level, what gives you confidence they will produce at the next level? Even a lousy team with an NFL caliber quarterback will show meaningful improvement. Inability to translate traits to production is, most likely, indicative of a quarterback lacking in mental side of the game.
I also find it ridiculous that you believe NFL general managers hinge on every word said by the "draftniks" at ESPN. Most fans with a brain recognize that they are entertainers who give us something to talk about leading up to the draft. You think Bill Belichick cares what Mel Kiper thinks? Doubtful. Furthermore, teams have zero incentive to reveal their interest in a potential franchise player. Hence, all the "anonymous scouts" who tear players down leading up to the draft.
*Anonymous AFC South scout: We love Watson's tape and his intangibles. He's our guy. We'll do whatever it takes to get him.*
What the ESPN hype machine/draftnik industrial complex really feeds on is not the proven, multi-year talents at big schools, like Watson, but the under-the-radar, small school sleeper. (Case in point, Wyoming quarterback Josh Allen). Hearing about the same old guys is boring. We need to hear about the new tight end from Southwestern Montana school of Mining who was a power forward for three years. Makes for a much better narrative.
Then we get to the traits. Based on your comments, I'm fairly certain you haven't actually watched the entire tape. "No velocity", "can only make about 3 throws", "can't read coverage", "doesn't have a natural feel for the qb position", but no evidence whatsoever to back up these claims. Watch the NC State or Appalachian State tape and you'll see him throw the ball 65 yards down the field with ease. Watch the tape from the 2014 Georgia game; one of his first throws was 40 yard touchdown stike to his receiver running the seam, bracketed by two defenders. Remember, this is an 18 year old kid playing his first college game in front of 90,000 fans, opening weekend, on primetime. Beyond the physical traits, watch the pre-snap adjustments and the blitz pickups. These are just a few examples. He can thrown the backshoulder, the fade, the skinny post, the slant, and has the requisite arm strength and accuracy to make every NFL throw. He has the physical AND the mental tools. I am not asserting that Watson will be an all-pro caliber quarterback. There are far too many variables in play to say definitively. But, of the quarterbacks in this draft, I would say he has the best chance.
Lastly, Johnny Manziel beat a different 'Bama team. Didn't you get the telegram? This is the best defense Nick Saban has ever had, if not the greatest defense college football has ever seen, and it was designed to stop the spread. The speed and athleticism at every position, the NFL talent, the aggressiveness; I can still hear Gary Danielson gushing. And to assert that it "wasn't a fair fight" in the 4th quarter (2017 that is) is just laughable. Was it not a fair fight in the 4th quarter of the super bowl? The greatest players assert themselves in the crucial moments on the biggest stages.