I'm certainly not a football authority - and I see this question asked all the time.
Arm strength.
WTF difference does it make if the QB is a slow decision maker - if his vision is too focused - if he can't put the ball where it needs to be?
Just how many long 40 plus yard passes do QB's make per game?
I may have a rifle that will accurately reach out and touch someone at 800-plus meters - but if I can't actually hit the SOB - what difference does it make how far that bullet will go?
A .22 Long Rifle round can go just about a mile in distance. We don't even shoot at targets at half that range.
What we need is a QB that can perform multiple critical tasks extremely effective in the 20-40 yard range in a timely manner, on a regular basis - as opportunities become open.
Then we won't need a steady stream of Hail Mary's - which at least to my game watching over the years - do NOT win that many games.
Because if guys are doing their jobs just - WELL, then we don't have to rely on heroic accomplishments.
He wouldn't be a QB if he can't throw some fairly long passes - but I'd suggest accuracy and vision are much more important.