Why is the CPU so unrealistic?

agree

my experience as Defense:
- some of my computer-controlled defenders stand around doing nothing while receivers run routes uncovered; it seems like they only start doing anything worthwhile after a completed pass;
- I once had a computer-controlled defender nearly directly in front of a rushing quarterback, about twenty yards away, doing absolutely nothing, with no other defenders nearby;
- even computer-controlled defenders that ARE covering somebody, they run around frantically like everything the receiver did is a total surprise;
- computer-controlled defenders, even when very close to a receiver, fail to intercept, or even disrupt the pass;
- one of my computer-controlled defenders standing next to a receiver in the End Zone, motionless, letting him receive a deep deep pass, and then tackling him after the touchdown was logged;
- two of my computer-controlled defenders, in the End Zone, charging a guy running for a touchdown near the sideline, the closer of the two in the End Zone could absolutely tackle him, but he stops suddently and sticks his arms out to the sides, the guy behind him crashes into him and can't go any further; no tackle, then touchdown;
- one of my computer-controlled defenders charging towards a Running Back and suddenly falling down to sit on the grass before reaching him;
- I'm pretty sure I even saw one of my defenders actively blocking (arm-in-arm) one of my other defenders who was trying to get to a runner;
- the computer offense almost always gets a complete pass, regardless of how much pressure there is on the quarterback and how many defenders are around the receiver;
- Running Backs on the computer's team sometimes get repeatedly smashed by multiple computer-controlled defenders, and never go down, with defenders bouncing off them like racquetballs;
- every player on Offense is faster than all my computer-controlled defenders; if they are wide open and receive a pass, it's a guaranteed completion followed by a guaranteed touchdown;

my experience as Offense: 
in short, the opposite...
- all my receivers are tightly covered by Computer defenders, all the time;
- each defender on the Computer's team reacts instantly to all movements by my receivers, as if they were tied together with a rope;
- if there is a defender anywhere near my receiver, the pass WILL be broken, and often intercepted;
- one of my receivers running right and ahead of the defender covering him by over a yard, pass to him with my quarterback from the right side of the field (the clear side), the defender leaps forward, body horizontal to the ground, and takes the ball from my receiver, who caught the pass in the stomach with both hands;
- similar to previous, except the defender was also behind the receiver in the sense that the receiver was between the defender and the ball, the defender leaps and snakes around and through my receiver's body to the front and somehow grabs the ball;
- my receiver catches a ball in the End Zone, completely in-bounds, with some defenders nearby, never drops the ball, never has the ball taken from him, and it was ruled an incomplete pass, with no possibility of challenge;
- if there is a defender on the imaginary line in the grass connecting the quarterback to the receiver, they will leap high up into the air and snatch the ball, interception, even if the receiver was very far away and therefore the ball was very high; my defenders never do that;
- each player on Defense is faster than all players on my Offense; in the rare cases that I find a wide open receiver, some defender rockets over to him and tackles him before he can run; no automatic touchdown for meeee;
- when a defensive linesman wants to leave his offensive linesman and tackle my Running Back or Quarterback, he just does it, my Offensive Linesman just lets him go; it was all voluntary;
- when receiving a kick, the first wave always goes through unobstructed and tackles me; I guess my guys were blocking somebody else;

finally, note that much of the above happened after I switched the "CPU Skill" for Defense stuff like interceptions down to 0 and my own to 100; there was no obvious effect on the game; the game I just played, in just the first half, I was intercepted 4 times and somehow fumbled a punt return once, they were intercepted 0 times and 0 fumbles

this is a game where learning and practice (and sliders) have no effect on the outcome