I think going to a full challenge replay system is an easy fix.
My other issue is the hurry up and wait. You want to go fast? Cool. I hate running up to the line so that the defense can't substitute, to then look over to the sidelines and stand there for 25 seconds signalling the play to everyone, while nothing happens.
I learned more football from the analysts breaking the previous play down during the huddle than from watching the game itself. Then I learned what to look for. That has been removed so we can watch a QB tap his helmet for 25 seconds, just in case he snaps the ball.
I'm not sure what the easy fix is to that though. The analytics show that you are better off running a simple offense against a gassed defense. Like most sports, the math has showed us that the most efficient way to play the game is generally the least enjoyable version. It's why basketball has turned into a 3 point shooting contest, and baseball is just a bunch of home runs and strike outs