They're mostly mental. He has trouble hitting receivers in stride; he has trouble "seeing" who is going to be open at the time of the catch even though the receiver is not open at the time of the throw; he can't put the ball in tight windows or place it so that a receiver can catch in stride and get a lot of YAC.
He has trouble seeing the center of the field. He hesitates to throw at all unless he sees someone wide open, usually at a dead stop or near a dead stop. Only then (usually) does he have confidence to throw the ball.
His mechanics are pretty bad; he has lots of bad habits he hasn't overcome so far; on occasion he throws off the wrong foot; he has happy feet; he taps the ball and hops around as he contemplates "what should I do" etc., instead of having the ball ready to go.
When he gets everything right and makes a lovely pass, he can't do it consistently time and time again. He's inconsistent.
He is a great athlete, and a great runner. Has great speed. He can almost always make the first man miss in the open field if he runs, and his ability to squirm out of a sack is outstanding. His natural arm strength is also excellent.
He protects the ball well, but that is a double edged sword. He doesn't throw many interceptions because he is hesitant to make a lot of passes a better QB would attempt. He needs to overcome that overly cautious nature if he is improve, but when he does gain more confidence, he'll throw more interceptions.
I like Tyrod, but most of the things he does well are not what I want my QB to do well.
What he struggles to do well is what your QB must be able to consistently do well, if you want to win the close ones, the tough ones, the ones where the D didn't show up, and the playoff games where every team you play has a QB of the type Tyrod is not.
Tyrod is a .500 ceiling, +/- a game or 2 QB. Can't see him winning a playoff game against a team with a good passer.