Practice mode is supposed to simulate an actual game. So why shouldn't the AI adjust if you're running the same play over and over again? You're just making excuses for the poor AI in Madden.
This video is one of the reasons why I haven't touched a Madden game in 4 or 5 years running now. You can win with the same garbage over and over again. Every team feels the same, and the differences between winning against a live person and not winning is do you know how to exploit the AI and can you control a player well enough to disrupt the other players ability to exploit the AI.