While what Valdarez says is true, I do think the op asks a valuable question.
I think a few things need happen to make a football video game both more immersive as well as more realistic.
1) Move away from an animation based system, which restrict you to pre-scripted movements. This needs to be something more dynamic. Look at the way randy moss runs. Look at how Brian Leonard dives for the first down marker. Blocking schemes..... I could go on...
2) Move away from subjective 0-99 player scaling. Anyone in the NFL will tell you, it's not the "measurables" that make a complete football player. Lets have a system to input the measurables like 40yrd times. And from there, a more advanced system needs to be implemented to determine things like decision making, etc....
3) More focus and variety on the coaching side of things. So much of making a winning team is done through coaching. There are a lot of great coaches in the NFL. Most often, what makes the best ones stand out is their ability to scheme faster than the competition can figure them out.
Look at how different the screen game looks for the Cowboys, Eagles, Colts, Browns, etc (IRL). That is a coach drawing up who is going to block who. While the central ideas may be the same, no two team's playbooks should be alike. As well coaches will use their teams to best work with the players they have, not just running the ball while they have the lead....
These three things are extremely complex things to consider writing in code. So much so, that I don't think it's realistic to expect things like this in a video game, unless a seriously motivated and football-fanatical game studio takes the reigns. I shudder at the notion of possibly explaining myself any further, as the subject of football is not shallow if you're trying to consider the game from the perspective of a head coach or GM.