There's around 15 younger quarterbacks coming into the league every year. The more time that goes by, the less likely he'll get a shot.
He should have switched positions while continuing to work with the QB coach on the side, or played in the CFL. Relishing his position as a bruising running back or wstd would have gone a long way in exhibiting his hunger and love for the game. That fact that he stubbornly took his ball and went home pretty much sealed his fate.
What position would he switch to? TE? Too short and one dropped pass and he is done - a position he has never played. Did any team even show any interest in him as a TE? Fullback/RB? Why and how? Has the NFL treated white rbs better? If Peyton Hillis struggles to make a roster how could Tebow? No NFL team wants him near the field in any aspect.
If we want to point to mistakes he made it would be being way too humble and also choosing the Jets over the Jaguars. He could have been a 4th stringer and hated by the coaches, but the fans would have forced Tebow to start just like they did in Denver. Jew York is last fan base that would support him.