Relying solely on the 1 game sample:
The Texas defense is for real. They have depth at every position. They'll make every game hard on the opponents.
The Texas offense has to pick up the aggression. The OL, particularly the interior guards, were in the right place, but were tentative and hesitant. They must trust their reps and execute violently.
Quinn needs to play like he's the only one on the field. I have no doubt he's drilled footwork and mechanics, but when he's in a game, he's looking around and too aware of the defense. He left a ton of yards by bricking throws I know he can make because he was too concerned with pressure that really wasn't there.
Unless the first half was just an aberration, the Texas offense isn't going to suddenly link up and boat race Alabama. Texas can win by smothering the Bama offense and grabbing easy points from field position. It's there to be had.