I see your point. I think that a successful team depends on whether it can run smoothly by assembling all parts. Not just add up all individual parts. For example, by weighing each of first team player of Inter Milan to those of Valencia, most of Inter Milan's players must be better. Then Inter would have won Valencia in ECL this year. However, Inter could not beat Valencia in both of the games. That means Valencia is a good machine when all parts work well with each other. But if you break it down, each of the parts may not work well in other machine.
When you change the defensive line of your squad, the attacking line may be affected as well. Then your attacking line is no longer as your strength while your defensive line may not be improved at the same time.
In other words, if your squad is an attacking tool, e.g. a gun, you must not use it as a shelter the prevent yourself from hitting by a sword. You must use the gun to attack your enemy in order not to let your enemy to hurt you.
I like such discussion anyway. Thank you