When I'm adding a new drill, exercise or small-sided game to a training session I know that the players will go through three separate phases of learning; first, they need to focus on the framework and rules of the activity, then they can pay attention to the technique that the activity requires. Only then can they play with the necessary speed and intensity that will replicate a game situation.
One of the biggest mistakes I see from coaches is a lack of attention and patience to the first two phases so that they can get to the final phase. They push players to play quickly and game like before theyfully understand the activity and before they can perform the required techniques cleanly with confidence. When they try to move too quickly from one phase to the next, the players don't fully benefit from the session and they don't see the concepts transfer to the next match. This results in a waste of training time and frustration for the coach and players.
I think that coaches often make this mistake because they only have a couple of practices per week and they are trying to teach a lot in a short period of time. My solution to this problem is to use activities that are straight forward and easy for the players to understand. There's no need to make it too complicated. The less time you have to spend teaching the exercise, the more time you can spend refining the technique to the point were the players are moving at game speed.
As players grow in experience it's important to teach more complex concepts. If the foundation has been laid soundly at the younger ages then you'll find that players can move quickly from the learning the exercise to playing at game speed because they have mastered basic techniques through years of patient practice.
Have a great day,