The Franchise Quarterback "stab" in the Draft, in my opinion, completely changes all arguments of this conversation.
If our current Quarterback was 35ish instead of 38ish then I'd be totally with you.
The fact that our 38 year old, banged-up at times, Quarterback is POTENTIALLY "year-to-year" puts the team at HEIGHTENED AWARENESS in scouring and searching for that next Franchise guy, pronto.
So when the opportunity arises to get that wholly important piece which could dictate 10 YEARS of the Franchise's being, if its someone that Snead/McVay like and believe in, you've got to take him.
Hate to break this down into middle-school terms, but if Simpson turns out to be "it," (a Top 10 Quarterback OR wins a Super Bowl with us as a middle-of-the-pack guy) it was a great pick.
If Simpson turns out to be NOT "it" ( middle-of-the-pack, doesn't lead us to high Playoffs OR an outright bust) then it was the wrong and horrendous pick.
Snead and McVay are betting on Simpson. We'll see how that plays. But the fact that "next Franchise Quarterback" is in the mix in this discussion more or less devalues your argument because of the obvious major importance of the position itself. Stafford's age plays a huge role in this.