You might also consider that Tebow at Denver was working with poor receivers. Good receivers in the NFL have catchable pass drop rates of 0 to 3 percent, e.g. Dez Bryant (1.6%) and Larry Fitgerald (3.6%).
Tebow at Denver had (mainly) Eric Decker and Demaryius Thomas. In 2011 their drop rates for catchable passes were 17% and 13.5% - near the bottom of the NFL receiver corps. If Tebow had had even above average receivers his completion rate would have been something north of 50 percent by my reasoning.
Also consider: Tebow got his team 6.38 yards per passing attempt in 2011. Blaine Gabbert had 5.36; Colt McCoy 5.9; Sam Bradford 6.06; Mark Sanchez 6.40.
You probably know this: In terms of TDs/INT in 2011 Tebow was 12-6; Bradford was 6-6; and McCoy was 14-11. In terms of win/loss Tebow was 7-4; Bradford 1-9; McCoy 4-9. In terms of game start experience thru 2011 Tebow had 14; Bradford 26; McCoy 21.
Net: Tebow did better with less game start experience in 2011 than some other brand-name quarterbacks that were drafted in the same year Tebow was (2010).
How'd they do next season with Peyton Manning?
Also consider: Tebow got his team 6.38 yards per passing attempt in 2011. Blaine Gabbert had 5.36; Colt McCoy 5.9
Is anyone here accusing Gabbert or McCoy of being NFL-caliber QBs? I'd agree they're probably still in the league - albeit as backups - because they 'look like' QBs more than Tebow is seen to.